Iran yesterday said its arch-foe the United States was "isolated" after a US unilateral declaration that UN sanctions are back in force against the Islamic republic was dismissed by other major powers. 

The Trump administration said the so-called "snapback" of the sanctions was in effect and threatened to "impose consequences" on any UN member state that fails to comply.

Iran's President Hassan Rouhani yesterday thanked UN Security Council members for standing firmly behind the deal and said that Washington's "maximum pressure" campaign against Tehran had thrown the US into "maximum isolation".

"America's maximum pressure against Iran, in its political and legal aspects, has turned into America's maximum isolation," Rouhani said during a televised cabinet meeting.

The sanctions in question were lifted in 2015 when Iran and six world powers -- Britain, China, France, Germany, Russia and the US -- reached a landmark nuclear deal known as the Joint Comprehensive Plan of Action.

But US President Donald Trump withdrew from the JCPOA in 2018, saying the deal -- negotiated by his predecessor Barack Obama -- was insufficient. He also renewed and even strengthened Washington's own sanctions.

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 Security Council member disputes Washington's ability to execute this legal pirouette, and the UN body has not taken the measure any further.

Yesterday, two permanent council members -- France and Britain -- issued a joint statement along with non-permanent member Germany saying the US's "purported notification" was "incapable of having any legal effect".

Russia also said the US lacked legal authority.

US Secretary of State Mike Pompeo announced Washington's latest move in a statement. Pompeo promised measures would be announced in the coming days against "violators" of the sanctions.

With around six weeks to go until the November 3 US election, Trump could unveil those measures in a speech at the UN General Assembly on Tuesday.

Iran's Foreign Minister Mohammad Javad 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.