President Donald Trump has warned that Iran is "playing with fire" after Tehran announced that it has exceeded the limit on enriched uranium reserves under the 2015 nuclear deal from which the US walked out last year.
His statement came as Secretary of State Mike Pompeo, in a strongly-worded statement, asked Tehran to halt enrichment of uranium.
Monday marked the first time Iran is known to have breached the terms of the deal.
The International Atomic Energy Agency confirmed Iran had exceeded the limit that the deal imposed on its stockpile of low-enriched uranium.
Trump told reporters at the White House that Iran is "playing with fire" as Secretary of State Mike Pompeo in a strongly worded statement asked Tehran to halt enrichment of uranium.
"The Iranian regime, armed with nuclear weapons, would pose an even greater danger to the region and to the world. The United States is committed to negotiating a new and comprehensive deal with the Iranian regime to resolve its threats to international peace and security," Pompeo said.
As long as Iran continues to reject diplomacy and expand its nuclear programme, the economic pressure and diplomatic isolation will intensify, he said.
Alleging that the Iranian regime has taken new steps to advance its nuclear ambitions, Pompeo said that the world's leading state sponsor of terrorism continues to use its nuclear programme to extort the international community and threaten regional security.
"No nuclear deal should ever allow the Iranian regime to enrich uranium at any level. Starting in 2006, the United Nations Security Council passed six resolutions requiring the regime to suspend all enrichment and reprocessing activity. It was the right standard then; it is the right standard now.
"The Trump administration calls on the international community to restore the longstanding nonproliferation standard of no enrichment for Iran's nuclear programme. Iran has the uncontested ability to pursue peaceful nuclear energy without domestic enrichment," Pompeo said.
Trump told reporters at the White House that he has no message for Iran, but they should know that they are playing with fire.
"No message to Iran. They know what they're doing. They know what they're playing with. And I think they're playing with fire. So, no message to Iran whatsoever," said the US President in response to a question.
In a separate statement, White House Press Secretary Stephanie Grisham said that the Iranian regime took action to increase its uranium enrichment.
"It was a mistake under the Iran nuclear deal to allow Iran to enrich uranium at any level. There is little doubt that even before the deal's existence, Iran was violating its terms. We must restore the longstanding nonproliferation standard of no enrichment for Iran. The United States and its allies will never allow Iran to develop nuclear weapons," she said.
"Maximum pressure on the Iranian regime will continue until its leaders alter their course of action. The regime must end its nuclear ambitions and its malign behaviour," Grisham added.
Under the 2015 nuclear deal, Iran had agreed to cap its stockpile of low-enriched uranium at 300 kilograms, one of the several restrictions on its nuclear activities, in exchange for the lifting of almost all international sanctions.
Iranian officials, however, said that they are violating the terms of the deal because the US withdrew and reimposed sanctions on Tehran.