WASHINGTON/BRUSSELS — President Donald Trump on Monday repeated his insistence that Iran will not be allowed to obtain a nuclear weapon, amid mounting tension over the US killing of a top Iranian commander.

Writing in all-caps, the US leader tweeted: "IRAN WILL NEVER HAVE A NUCLEAR WEAPON!" The tweet came a day after Tehran announced it was further winding down observance of parts of an international deal struck to ensure that the country does not secretly develop a nuclear weapon under cover of its civilian nuclear industry. Trump withdrew the United States from the 2015 deal negotiated under his predecessor Barack Obama. Last year, Iran resumed uranium enrichment, reporting a tenfold increase in production.

Tensions between the two countries spiked last week when a US drone strike in Baghdad killed Qasem Soleimani, the head of the Iranian Revolutionary Guards' Quds Force. While Iran has threatened retaliation for the killing, Trump has warned that the US will strike "very hard and very fast" at as many as 52 Iranian targets if the Islamic republic does attack US personnel or assets.

Huge crowds turned out Monday in Iran for the 62-year-old commander's funeral, while in neighboring Iraq, parliament has voted to expel some 5,200 US troops stationed in the country. Trump's tweet did not add any details about steps he was considering to prevent Iran from reviving its nuclear program. Iran has always denied any military dimension to its nuclear project.

Meanwhile, EU foreign ministers will hold emergency talks on the Iran crisis on Friday, diplomats said, as tensions rise after US forces killed an Iranian general in a drone strike.

The announcement on Monday came after the EU's diplomatic chief voiced regret at Iran announcing another step away from the fragile 2015 nuclear deal, as Tehran seethes over the killing of Qasem Soleimani, head of the Revolutionary Guards' covert Quds Force. Josep Borrell, the EU's high representative for foreign affairs, tweeted that the accord, which has been teetering on the brink of collapse since US President Donald Trump withdrew support, was "now more important than ever". European-led efforts to keep Iran in the deal — which curbed its nuclear program in return for sanctions relief — have borne little fruit since Trump's decision in May 2018 to pull out and reimpose sanctions. Borrell will lead a meeting of foreign ministers at 2.00 p.m. (1300 GMT) on Friday, three diplomats said, to discuss the fallout from the Soleimani killing and the future of the nuclear deal.

Borrell said the bloc would wait for further details of Iranian breaches from the International Atomic Energy Agency (IAEA) before deciding how to respond.

"Deeply regret Iran's latest announcement on #JCPOA. As ever we will rely on @iaeaorg verification," Borrell tweeted, using an abbreviation for the deal's formal name. "Full implementation of #NuclearDeal by all is now more important than ever, for regional stability & global security. I will continue working with all participants on way forward." On Sunday, Iran said it would forego the "limit on the number of centrifuges" it had pledged to honor in the 2015 agreement, casting doubt on an EU push for talks to salvage the deal. Borrell spoke to Iranian Foreign Minister Mohammad Javad Zarif at the weekend and issued a personal invitation to come to Brussels, but so far Iran has not given a public response. EU spokesman Peter Stano said there was "a lot of activity going on" from the bloc as it seeks to help defuse tensions. European Commission President Ursula von der Leyen was expected to make a statement on the situation later on Monday, while NATO has convened an extraordinary meeting of its ruling North Atlantic Council to discuss the crisis — in particular on the future of its training mission in Iraq. In another development, US lawmakers will vote in coming days on a war powers resolution aimed at putting a check on Donald Trump's military actions after he ordered the killing of Soleimani, a senior Democrat said. House Speaker Nancy Pelosi announced the plan to introduce and vote on the resolution "to limit the president's military actions regarding Iran," in a letter to colleagues late Sunday.

The measure, she explained, "reasserts Congress' long-established oversight responsibilities by mandating that if no further congressional action is taken, the administration's military hostilities with regard to Iran cease within 30 days." Pelosi said the killing put US troops and civilians in danger by "risking a serious escalation of tensions with Iran." Democrats have complained that Trump took the action without first consulting with the so-called Gang of Eight top lawmakers in Congress, including Pelosi, and have insisted that only Congress can declare war.

"As members of Congress, our first responsibility is to keep the American people safe," Pelosi said in her letter. "For this reason, we are concerned that the administration took this action without the consultation of Congress and without respect for Congress' war powers granted to it by the Constitution."

Meanwhile, Moscow on Monday urged parties to the Iran nuclear deal to treat salvaging the agreement as a "priority", calling on European partners to fulfill their obligations to ensure Iran stays committed to the accord. "Keeping the broad agreements and ensuring their sustained implementation must remain a priority task for all partners," the Russian foreign ministry said in a statement. It said the announcement by Tehran of a further rollback of its commitments, by foregoing the limit on the number of centrifuges, "does not carry any threat from the point of view of nuclear weapon proliferation". Moscow pointed out "holes" in the approach to the deal by other parties.

"We hope that the necessary outcomes will be achieved. A lot depends on our European colleagues," it said. Russia "keeps full commitment" to the deal and is "ready to continue work" on it, the statement said, calling on "political will and a decisive collective response" from others. "We are certain that when these challenges are overcome, the Iranian side will have no reason to deviate from the agreed-upon demands," it said. Russia's Defense Minister Sergei Shoigu on Monday spoke with the chief of Iranian General Staff Mohammad Bagheri on "avoiding escalation of the situation in Syria and the Middle East due to the murder" of Soleimani. — AFP