Iran said Sunday the United States is facing "maximum isolation" after major powers dismissed a unilateral US declaration that UN sanctions on Tehran were back in force.
The administration of US President Donald Trump said the sanctions had been re-activated under the "snapback" mechanism in a landmark 2015 nuclear treaty -- despite Washington having withdrawn from the deal.
As other signatories cast doubt on the move having any legal effect, Washington threatened to "impose consequences" on states failing to comply.
But Iran's President Hassan Rouhani said a concerted campaign by Washington to pressure Tehran had backfired.
"We can say that America's 'maximum pressure' against Iran, in its political and legal aspect, has turned into America's maximum isolation," he said in a televised cabinet meeting.
He praised the UN Security Council's approach to the issue as "very valuable" as it ignored "America's request (and) held no session to consider their request".
The Security Council was what "the Americans always thought of as their point of strength," he said.
The sanctions in question had been lifted when Iran, the five permanent members of the UN Security Council (Britain, China, France, Russia and the US) and Germany signed the 2015 treaty on Iran's nuclear programme, known as the Joint Comprehensive Plan of Action.
But Trump withdrew the US from the JCPOA in 2018, saying the deal -- negotiated by his predecessor Barack Obama -- was insufficient.
He also renewed and strengthened Washington's own sanctions as part of a "maximum pressure" campaign against the Islamic republic.
The US insists it is still a participant in the agreement that it stormed out of -- but only so it can activate the snapback option, which it announced on August 20.
Virtually every other UNSC member disputes Washington's ability to execute this legal pirouette, and the UN body has not taken the measure any further.
On Sunday, France, Germany and Britain issued a joint statement saying Washington's "purported notification" was "incapable of having any legal effect".
Russia also said the US lacked legal authority and that its "illegitimate initiative and actions" could not have "international legal consequences" for others.
Rouhani thanked UNSC members who had "stood against America's illegal request" and said if remaining signatories let Iran access the deal's economic benefits, Iran would reinstate nuclear commitments it had dropped in response to the US withdrawal.
Iran's foreign ministry brushed off the US move and called on the rest of the world to unite against what it called America's "reckless actions".
"I imagine these are the most bitter days and hours for" the US, said spokesman Saeed Khatibzadeh.
US Secretary of State Mike Pompeo, announcing the move, said Washington "welcomes the return of virtually all previously terminated UN sanctions on the Islamic Republic of Iran".
He said further measures would be announced in the coming days against sanctions "violators", to ensure that "Iran does not reap the benefits of UN-prohibited activity".
Iran's Foreign Minister Mohammad Javad Zarif hit back, tweeting "the world says NO Security Council sanctions were restored".
But, he added, Pompeo "threatens to punish a world that refuses to live in his parallel universe".
With around six weeks to go until the US presidential election, Trump could unveil those measures in a speech at the UN General Assembly on Tuesday.
But Iran's foreign ministry said Washington, by leaving the nuclear deal, had "explicitly denied itself any right" to use the "snapback" mechanism.
It also warned that if the US "acts on these threats, directly, or with the cooperation of a handful of its puppets, it will face a serious response and be responsible for all the dangerous consequences".
The US had already suffered a resounding defeat at the Security Council in mid-August, when it tried to extend an embargo on conventional weapons deliveries to Tehran, which was due to expire in October.
Pompeo responded with an unusually vehement attack on Britain, France and Germany, accusing them of "siding with Iran's ayatollahs", before announcing the snapback.
In Washington's eyes, its move has now extended the embargo "indefinitely" and reactivated international sanctions on many activities related to Tehran's nuclear and ballistic missile programmes.
Zarif accused Pompeo of not having read UN resolutions or the nuclear deal.
"He's now probably waiting for the movie to come out so he can begin to understand it," he told state television.
On the streets of Tehran, Iranians complained of harsh economic conditions they blamed on US sanctions.
"It's really difficult for the people right now. Whether sanctions are reimposed or not, we are living with utmost difficulty," said Leila Zanganeh, a martial arts instructor.
But Danial Namei, an architect, seemed to care little for returning UN sanctions and doubted things could get worse.
"We've been through difficult things and it is still ongoing. There's nothing worse than the worst, after all," he said.