Executive Summary
During April–May 2026, Iran and the United States engaged in mediated ceasefire talks in Islamabad, Pakistan. New evidence suggests Iran used the pause in hostilities to replenish key weapons. Satellite images have revealed Iranian warplanes and hidden missiles reemerging, and U.S. intelligence reported Chinese arms shipments to Tehran (Reuters, 2026b; Som, 2026). Official statements from Iran’s leadership and Pakistan’s government reflect mixed responses about these developments. This analysis surveys the latest reports (April–May 2026) on Iranian rearmament during the Islamabad talks, reviews legal constraints, and assesses the implications for regional security.
Background: Islamabad Talks and Ceasefire
In early April 2026, Pakistan’s Prime Minister Shehbaz Sharif and military leadership brokered a two-week ceasefire between the United States and Iran, with Islamabad proposed as the venue for negotiations. U.S. President Donald Trump announced his acceptance on Truth Social, stating the ceasefire had been mediated by Pakistan’s Prime Minister and its military chief, and that Iran had put forward a 10-point proposal as the basis for further talks (CNN, 2026; Madan and Biswas, 2026). Pakistan’s Prime Minister Shehbaz Sharif expressed hope the talks would “succeed in achieving sustainable peace” (Madan and Biswas, 2026). From April 11–12, high-level officials — including U.S. Vice President J.D. Vance and Iran’s parliament speaker Mohammad Bagher Ghalibaf — met for marathon negotiations.
After 21 hours without a deal, Vance said Iran had “chosen not to accept our terms” and declared the talks a failure (Al Jazeera, 2026). In response, President Trump announced on April 12 that a naval blockade of Iranian ports would begin on April 13 at 10:00 a.m. Eastern Time (CENTCOM, 2026). Iran’s government responded cautiously: Foreign Ministry spokesperson Esmaeil Baghaei said “no one had such an expectation” of a quick agreement (Al Jazeera, 2026), and Speaker Ghalibaf stressed that Tehran had floated “forward-looking” proposals, but that Washington had yet to earn Iran’s trust (Al Jazeera, 2026).
Evidence of Rearmament
Concurrently, multiple sources report that Iran’s forces were quietly regenerating combat power. These indicators include satellite imagery, intelligence reports, and official admissions.
Satellite Imagery of Hidden Missile Bases
CNN reported that before and during the ceasefire, satellite photos showed heavy machinery clearing tunnel entrances at Iran’s underground missile launch sites (Iran International, 2026). Experts note these “missile city” tunnels were built to survive strikes and then allow forces to re-emerge (Iran International, 2026). U.S. intelligence estimated that roughly half of Iran’s missile launchers survived earlier strikes, some remaining buried underground (Iran International, 2026). Clearing debris from these sites means Iran can restore missile batteries that had been neutralized, effectively reconstituting lost air defenses.
Intelligence on Chinese Arms Shipments
U.S. intelligence reportedly learned that China was preparing to send new air-defense weapons to Iran during the ceasefire (Reuters, 2026b). According to Reuters, the shipment included shoulder-fired MANPADS (surface-to-air missiles) meant to bolster Iran’s short-range air defense (Reuters, 2026b). President Trump himself warned China that “China can have big problems” if it delivered such arms (Reuters, 2026b). Indian media also cited regional intelligence claims that China was supplying Tehran with a range of weaponry — advanced MANPADS, precision-guided munitions, and satellite targeting data — to replenish its stocks (Dheman, 2026).
Iranian Military Aircraft in Pakistan
Open-source satellite images confirmed that Iran moved aircraft into Pakistan during the ceasefire. On April 25, 2026, a Vantor/Maxar image published by NDTV on May 13, 2026, showed an Iranian Air Force C-130 transport parked at Pakistan’s Nur Khan Airbase, approximately 10 kilometres from central Islamabad (Som, 2026). This corroborated a CBS News investigation. Pakistan’s government acknowledged some transit of aircraft after the ceasefire, but its foreign ministry called media reports of a secret buildup “misleading and sensationalized” (Som, 2026). U.S. officials believe Iran shifted multiple aircraft into Pakistan to hide them from further U.S. strikes (GlobalSecurity, 2026). U.S. Senator Lindsey Graham told military leaders he no longer trusted Pakistan as mediator if it had sheltered Iranian jets (Som, 2026).
Figure: Satellite image of an Iranian C-130 transport at Pakistan’s Nur Khan Airbase (Chaklala), April 25, 2026 (Vantor/Maxar, published by NDTV, 13 May 2026). This supports U.S. claims that Iranian warplanes were parked in Pakistan during the ceasefire talks (Som, 2026).
Statements by Iranian Officials
Some Iranian figures openly indicated a focus on military preparedness. Vance said Iran was unwilling “to accept our terms” (Al Jazeera, 2026), while Iran’s Foreign Ministry countered that extending talks was realistic and expected (Al Jazeera, 2026). Ghalibaf, who led the Iranian delegation, stated in social media remarks that Iran had presented “forward-looking” initiatives and that the U.S. must now earn Iran’s trust (Al Jazeera, 2026). An Iran International analysis cited an IRGC intelligence post noting “widespread frustration” among U.S. troops, implying Iranian strikes were keeping American forces on edge (Iran International, 2026). In an April 14 interview, Dr. Hamidreza Marandi, an adviser to foreign affairs, warned that Iran was “very busy preparing ourselves for the next round of war” and accused Washington of “bolstering its military capabilities while we are at the negotiating table” (Zanger-Nadis, 2026).
U.S. Intelligence and Analysis
U.S. officials have acknowledged Iran retained significant capabilities. In congressional testimony, Defense Intelligence Agency officials noted that Iran retains thousands of missiles and rockets (GlobalSecurity, 2026). In separate testimony, Marine Corps General Eric Caine said Iran’s forces were “weaker and less capable than in decades,” though that assessment predates the latest replenishment. Analysts note that Iran’s reconstitution of air defenses is a logical step for any military surviving intense strikes (GlobalSecurity, 2026).
Taken together, the evidence points to a significant Iranian effort to rearm during the Islamabad ceasefire. Open-source imagery confirms at least one heavy transport was hidden in Pakistan, and remote sensors show buried launchers being uncovered. U.S. warnings about Chinese-supplied weapons and domestic analyses caution that Iran’s battlefield losses are being replaced. The consensus among analysts is that Iran is not passive during negotiations: it is actively rebuilding its military capabilities.
Legal Context: Sanctions and Arms Controls
Iran’s arms build-up during talks occurs in a complex legal landscape. Under UN Security Council Resolution 2231 (2015), which endorsed the 2015 nuclear deal, all UN arms embargoes on Iran were set to end by October 2023 (Arms Control Association, 2026). However, in August 2025, European Security Council members invoked a “snapback” mechanism to reimpose the UN sanctions lifted in 2015 (Arms Control Association, 2026). As of late 2025, all prior UN restrictions — including bans on exporting conventional arms and missiles to Iran — are again legally in force (Arms Control Association, 2026). This means any transfer of new offensive weapons to Iran by third parties would violate UN mandates. Separately, Iran is party to the Nuclear Non-Proliferation Treaty (NPT), but has not signed the Arms Trade Treaty. Major powers, including the U.S. and EU, still embargo most arms sales to Iran under their own laws.
Despite these rules, enforcement is lax in wartime. Neither China nor Pakistan acknowledge UN or U.S. restrictions on their military interactions with Iran. Pakistan’s official line is that any planes in its bases were purely for diplomacy. China defends arms sales as bilateral commerce. On May 8, 2026, the U.S. Treasury sanctioned three Chinese satellite-imagery firms for providing the IRGC with high-resolution reconnaissance (GlobalSecurity, 2026), implicitly confirming that Iran was using foreign assets to bolster its military picture. The legal framework is overshadowed by realpolitik: Iran frames rearmament as self-defense, while Washington sees such moves as bad faith given the ceasefire.
Implications and Reactions
This rearmament drive has already influenced international reactions. In Washington, lawmakers have pointed to Iran’s rebuilt arsenal as evidence Tehran is not deterred. Senator Lindsey Graham warned the U.S. should “look for somebody else to mediate” if Pakistan is sheltering Iranian jets (Som, 2026). Defense leaders argue that Iran’s remaining missile stocks complicate U.S. targeting. Meanwhile, President Trump’s blockade of Iranian shipping is intended to pressure Tehran for concrete commitments.
In Iran, hardliners framed the ceasefire as a strategic win, highlighting Iranian demands such as lifting sanctions and preserving naval sovereignty (CBS News, 2026a). However, Iranian officials also signaled willingness to continue talks: Foreign Ministry spokesperson Baghaei said regional contacts would go on (Al Jazeera, 2026). The question now is whether future talks can resume with trust intact. Many analysts caution that Iran’s offensive buildup undermines confidence, suggesting Tehran sees itself in a protracted conflict rather than close to a settlement.
Analysis and Implications
During the ceasefire and talks, Iran clearly prioritized restoring its military. From an Iranian standpoint, this is rational: Tehran faces existential threats and is shoring up defenses regardless of the diplomatic track. Analysts argue Iran’s actions are “consistent with the behavior of any military organization” under attack (ISW, 2026). Internationally, however, these moves raise doubts. The U.S. and Israel may question Iran’s sincerity, seeing the rearmament as evidence Iran is only pausing to regroup. Pakistan’s neutrality has been strained; U.S. lawmakers openly criticized Islamabad for hosting Iranian aircraft.
The legal backdrop complicates matters. If the UN arms embargo is indeed in force post-snapback, then foreign aid to Iran’s military — whether Chinese missiles or aircraft sheltered in Pakistan — would violate UN mandates. Yet enforcement is politically fraught. Meanwhile, even without new imports, Iran’s domestic industry in drones and ballistic missiles continues expanding. Any future agreement must account for the enhanced Iranian arsenal. In effect, Iran has raised the cost of renewed conflict: U.S. and allied forces will face a more capable adversary if diplomacy fails. Conversely, knowing Iran is rearming might pressure Tehran to accept constraints in order to lift sanctions. In short, Iran’s arms build-up during the Islamabad talks is a gamechanger that undercuts trust but also underscores the urgency of a settlement.
As of mid-to-late May 2026, the diplomatic picture has shifted considerably, even as Iran’s reconstituted military capacity remains intact. By early May, U.S. envoys Steve Witkoff and Jared Kushner were negotiating a one-page, 14-point memorandum of understanding (MOU) with Iranian counterparts that would declare an end to the war and open a 30-day window for detailed talks on nuclear limits, Hormuz transit, and sanctions relief (Axios, 2026a). The proposed MOU included an Iranian commitment to a moratorium on uranium enrichment, with the U.S. demanding 20 years and Iran countering with five, and a compromise of approximately 12 years reportedly under discussion (Time, 2026b). On May 6, the White House said this was the closest the two sides had been to an agreement since the war began (Axios, 2026a).
However, Iran’s public posture remained cautious, with officials offering a more pessimistic assessment than their American counterparts (Time, 2026b). The situation escalated sharply on May 17, when Trump set five preconditions for resumed negotiations, including the delivery of 400 kilograms of enriched uranium to the United States and the limitation of Iranian nuclear facilities to a single operational site (CBS News, 2026b). On May 18, Trump announced on Truth Social that he had cancelled a “scheduled attack” on Iran planned for May 19, citing requests from Gulf states including Qatar, Saudi Arabia, and the UAE, and stating that “serious negotiations are now taking place” (Time, 2026c).
A Pakistani diplomatic source simultaneously confirmed to Reuters that a revised Iranian proposal had been passed to U.S. representatives, though noting that both sides continued to “change their goalposts” (CBS News, 2026b). The tactical picture as of May 20 is therefore one of continued dual blockade, intermittent ceasefire violations, and a narrow but open diplomatic channel — all while Iran’s missile forces and air defenses, partly rebuilt during the Islamabad pause, remain a standing variable in any scenario that follows a breakdown in talks.
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