Iran’s currency nosedived to an all-time low Sunday as the United States claimed it was ready to enforce all international sanctions against the country, while most of the world brushed off the U.S. move and acted as if nothing had changed.

The U.S. declaration that all sanctions against Iran are back in place as of Saturday night ushers in a new period of uncertainty and tension. The United States is almost alone in asserting it has the authority to reimpose the multilateral sanctions because it was an original participant in the 2015 nuclear agreement. Only a handful of countries agree.

It remains unclear how the administration will go about unilaterally enforcing the “snapback” of multilateral sanctions. Most countries say Washington stopped being a participant in the landmark deal with Iran when President Trump withdrew from it two years ago and began reimposing U.S. sanctions.

Traditional U.S. allies in Europe have pledged to actively ignore what the United States is trying to do, fearing that the Trump administration is looking for a way to kill the agreement with Iran it has been railing against for years. That could prompt Iran to kick out the international experts who have been given access to monitor its nuclear facilities.

The foreign ministers of France, Britain and Germany, which helped negotiate the deal, underscored their rejection of the U.S. position in a joint statement Sunday, saying the United States gave up its right to have a say in U.N. sanctions. Josep Borrell, the foreign policy chief of the European Union, pleaded for the agreement to be preserved and urged all parties “to refrain from any action that could be perceived as an escalation in the current situation.”

Trump is expected to issue an executive order Monday specifying how Washington will enforce punishment for violators. The State and Treasury departments will spell out penalties for businesses and individuals.

No one disputes that Iran has been violating some of the rules it agreed to. It was fulfilling them until the United States began reimposing U.S. sanctions in 2018. In response, Iran has gradually exceeded limits for enriched uranium and heavy water.

Iran’s infractions were the justification used by Secretary of State Mike Pompeo last month when he notified the U.N. Security Council that the administration was triggering snapback sanctions under a clause in the agreement it is no longer a party to.

Pompeo, in a statement released Saturday as the sanctions were declared to be in effect, said he expects all countries in the U.N. to fully comply. He took a harsher tone Sunday, calling the agreement negotiated by the Obama administration “nuts, absolutely nuts” and accusing European countries of not having “lifted a finger” to stop an arms embargo against Iran from expiring. But he expressed hope that European allies would “get on board” by backing the U.S. stance on confronting Iran over nuclear enrichment and arms sales.

“They know we’re right,” Pompeo said on Fox News’s “Sunday Morning Futures,” adding that the Europeans acknowledge privately that they don’t want Iran to resume arms sales but haven’t done anything to prevent it. “I hope they’ll join us. I hope they’ll get to the right place. They’re still wedded to this silly nuclear deal that was signed now five years ago.”

Though Tehran reacted with bravado, the signals were mixed. The Iranian rial plummeted to a historic low of 272,500 to the U.S. dollar. It had traded at 32,000 to the dollar when Iran signed the 2015 agreement limiting its nuclear program in exchange for sanctions relief.

But Iran’s Foreign Ministry spokesman, Saeed Khatibzadeh, sounded defiant, saying snapback sanctions exist only in “the fantastical world” of the Trump administration.

“They are attempting to make everyone believe it, but nobody is buying it except for themselves,” Khatibzadeh said during his weekly news briefing Sunday. “It is a television show whose sole presenter, viewers and those cheering it on are Mr. Pompeo himself and a handful of others.”

Lecturing the United States for its moves, he added, “Tehran’s message to Washington is clear: Return to the international community, return to your commitments, and stop bullying so the international community will accept you.”

The U.S. action is likely to cause some awkwardness this week at the U.N. General Assembly, which is commemorating its 75th anniversary. Most of the proceedings will be conducted virtually, with almost no world leaders attending because of the coronavirus pandemic.

Secretary General António Guterres said in a letter obtained by the Associated Press that he will not support the snapback sanctions unless they are approved by the Security Council, which overwhelmingly refused to do so last month.