(Bloomberg) -- Iran said it had exceeded limits set on its enriched-uranium stockpile, a move that risks the collapse of the 2015 nuclear accord and raises concerns that a standoff with the U.S. could lead to military action.“As I was informed, Iran has crossed the 300-kilogram cap according to plan,” the Iranian Students’ News Agency cited Foreign Minister Mohammad Javad Zarif as saying. “We have clearly expressed what we are doing and will act upon it,” he said, saying the step was in line with Iran’s rights under the agreement after it was abrogated by the U.S.The breach is likely to heighten tensions in the Persian Gulf that have spiked since the Trump administration exited the nuclear accord a year ago and reimposed crippling sanctions on Iran, prompting a warning that Tehran will ditch elements of the deal unless it’s given an economic lifeline by July 7. Attacks in the Strait of Hormuz, a vital waterway for oil shipments from the Middle East, and the Iranian downing of an American drone have raised concerns of another war in the region.Foreign Ministry Spokesman Abbas Mousavi said earlier on Monday that if European nations working to salvage the nuclear deal “take more concrete steps, Iran’s action in cutting back on its commitments can be rolled back,” according ISNA.The move was “carefully calibrated” by authorities and “isn’t in itself dangerous because it can be reversed,” said Sanam Vakil, senior research fellow at Chatham House Middle East and North Africa Program. “It’s the action and reaction and what comes next -- it’s a step in what can be a slippery slope.”International Atomic Energy Agency spokesman Fredrik Dahl confirmed that Iran’s stockpile of low-grade enriched uranium exceeded 300 kilograms (661 pounds).Iran was expected to breach the cap on Thursday, though it had appeared to back off from its warning following efforts led by European nations to preserve the accord. Seven more European countries agreed on Friday to support the U.K., Germany and France in rolling out a trade mechanism, known as Instex, that aims to protect trade with Iran from U.S. sanctions. Diplomats said the first transactions using the vehicle had been processed.European powers opposed President Donald Trump’s decision last year to quit the multinational accord intended to curb Iran’s nuclear development in exchange for easing sanctions. But they have been so far unsuccessful developing effective ways to maintain economic relations that avoid the U.S. banking system and the sanctions that Trump reimposed.At the same time, they had called for Iran to continue adhering to the accord, knowing that any violation would put European leaders in a difficult position with regard to U.S. officials.Tehran “has been escalatory in pushing Europe to challenge the Trump administration” and European nations are “struggling to find a band aid” to keep the agreement alive, Vakil said.The spokesman for Prime Minister Theresa May said the cap announcement was “extremely concerning” but the U.K. was working to keep the deal in place. Still, Britain’s commitment to the accord “relies on Iran complying with the full terms of the deal,” James Slack told reporters.The nuclear deal was designed to prevent Iran from breaking out and constructing a weapon within a year, as the U.S. and its allies feared. The Arms Control Association, a Washington nonprofit, estimates Iran would need about 1,050 kilograms (2,315 pounds) of uranium enriched to 3.67% to build one bomb. The material would then need to undergo further enrichment.Trump says he wants to negotiate a better deal that would also restrict Iran’s missile program and support for armed proxies around the region. But Iran says it can’t negotiate by force and while its economy and -- more recently -- its leaders are targeted by the U.S.Read more: A QuickTake on Iran’s nuclear program“It was a mistake under the Iran nuclear deal to allow Iran to enrich uranium at any level,” the White House said in a statement. “Maximum pressure on the Iranian regime will continue until its leaders alter their course of action.”Russia said on Monday that Iran’s move to breach the limit on enriched uranium wasn’t a surprise, blaming the U.S.’s policy of maximum pressure.Deputy Foreign Minister Sergei Ryabkov said Iran is confronting “unprecedented and unthinkable” U.S. efforts to throttle its economy, state news service RIA Novosti reported. At the same time, the leading Russian diplomat urged Iran to show restraint, voicing alarm at signals from Tehran it might pull out of the Treaty on the Non-Proliferation of Nuclear Weapons.(Updates with White House statement in 14th paragraph.)--With assistance from Golnar Motevalli, Arsalan Shahla, Boris Groendahl, Thomas Penny and Henry Meyer.To contact the reporters on this story: Nour Al Ali in Dubai at firstname.lastname@example.org;Ladane Nasseri in Dubai at email@example.comTo contact the editors responsible for this story: Benjamin Harvey at firstname.lastname@example.org, Joshua Gallu, Justin BlumFor more articles like this, please visit us at bloomberg.com©2019 Bloomberg L.P.