LONDON — Iran, Russia and European leaders roundly condemned President Trump’s decision on Friday to disavow the Iran nuclear deal, saying that it reflected the growing isolation of the United States, threatened to destabilize the Middle East and could make it harder to resolve the growing tensions on the Korean Peninsula.

The reaction was far from panicked, as Mr. Trump’s decision punts to Congress the critical decision of whether the United States will reimpose sanctions on Iran — a step that would effectively sink the deal.

But Mr. Trump also warned that unless the nuclear agreement was altered and made permanent — to prohibit Iran from ever developing nuclear weapons — he would terminate the agreement, an ultimatum that threw the future of the accord into question.

Though they avoided direct criticism of Mr. Trump, Prime Minister Theresa May of Britain, Chancellor Angela Merkel of Germany and President Emmanuel Macron of France said in a rare joint statement that they “stand committed” to the 2015 nuclear deal and that preserving it was “in our shared national security interest.”