In defiance of overwhelming opposition, the United States is preparing to declare that all international sanctions against Iran have been restored. Few countries believe the move is legal, and such action could provoke a credibility crisis at the United Nations.

Virtually alone in the world, the Trump administration will announce on Saturday that U.N. sanctions on Iran eased under the 2015 nuclear deal are back in force. But the other members of the U.N. Security Council, including U.S. allies, disagree and have vowed to ignore the step. That sets the stage for ugly confrontations as the world body prepares to celebrate its 75th anniversary at a coronavirus-restricted General Assembly session next week.

The question is how the Trump administration will respond to being ignored. It already has slapped extensive sanctions on Iran, but could impose penalties on countries that don't enforce the U.N. sanctions it claims to have reimposed. A wholesale rejection of the U.S. position could push the administration, which has already withdrawn from multiple U.N. agencies, organizations and treaties, further away from the international community.

In the midst of a heated campaign for reelection, President Donald Trump plans to address Iran in a speech to the General Assembly on Tuesday. Officials say he will also touch on his brokering of agreements for Israel and the United Arab Emirates and Bahrain to normalize relations in part to solidify a regional bulwark against Iran.

And, as he seeks to demonstrate statesmanlike credentials ahead of the election, Trump has injected another element of uncertainty into the mix by threatening to retaliate “1,000 times” harder against Iran if it attacks U.S. personnel overseas.

His tweeted warning came earlier this week in response to a report that Iran is plotting to assassinate the U.S. ambassador to South Africa in retaliation for the U.S. killing of a top Iranian general at the beginning of the year. Neither Trump nor any other senior U.S. official has confirmed such a plot exists, although they have said Iran has a long history of political assassinations.

Amid uncertainty over that, the other 14 members of the Security Council and all but about five of the U.N.'s 195 member states say the U.S. lost its legal standing to act on sanctions when Trump withdrew from the nuclear accord more than two years ago. The U.S. argues it retains the right to enact the “snapback” of sanctions because the council resolution that endorsed the deal refers to it as a participant.

“These will be valid U.N. Security Council (actions) and the United States will do what it always does, it will do its share as part of its responsibilities to enable peace,” Secretary of State Mike Pompeo said on Wednesday. “We’ll do all the things we need to do to ensure that those sanctions are enforced.”

Pompeo traveled to the United Nations on Aug. 20 to formally notify the Security Council that the U.S. was triggering snapback because Iran is not complying with the nuclear deal. He dismissed suggestions that the administration was engaged in anything legally questionable or even controversial.

He said the snapback mechanism was the “one thing that the previous administration got right” in the nuclear deal that Trump has denounced as the worst deal ever negotiated. The agreement was a signature foreign policy achievement of President Barack Obama and gave Iran billions of dollars in sanctions relief in exchange for curbs on it nuclear program.

Yet, aside from Israel and the Gulf Arab states, almost no country in the world agrees with the U.S. Russia and China, along with American allies Britain, France and Germany, who often disagree but remain parties to the 2015 agreement, are united in declaring the U.S. action “illegal.”

Nonetheless, the U.S. special envoy for Iran, Elliott Abrams, told reporters Wednesday that all U.N. sanctions would “snap back" at 8 p.m. EDT on Saturday.

”We expect all U.N. member states to implement their member state responsibilities and respect their obligations to uphold these sanctions,” Abrams told reporters.

“If other nations do not follow it,” he said, “I think they should be asked ... whether they do not think they are weakening the structure of U.N. sanctions.”

U.N. diplomats said the three European countries remaining in the Joint Comprehensive Plan of Action, or JCPOA, who are all currently Security Council members, will likely respond by issuing a statement reiterating their position that the United States cannot trigger snapback.

Trump administration officials been attacking the 2015 nuclear deal for years. They say it is fatally flawed because certain restrictions on Iran’s nuclear activity gradually expire and will allow the country to eventually develop atomic weapons.

The U.N. sanctions the U.S. is seeking to reimpose include a ban on uranium enrichment, all missile activity, and the indefinite extension of an arms embargo that would otherwise expire on Oct. 18. The Security Council rejected a U.S. effort to extend the embargo in a lopsided vote that got support from only one country, the Dominican Republic.

Pompeo reiterated Wednesday that Iran “remains the world’s largest state sponsor of terrorism and we don’t believe that them being able to trade in weapons of war with impunity is remotely acceptable.” He called the U.S. decision to reimpose sanctions “good for the peoples of all nations.”

But opposition to the U.S. move is widespread and strong, including from 13 of the other 14 Security Council members.

“Under intl law you can’t withdraw from an agreement and then claim you can still benefit from its provisions. Under 'rules-based intl order where the rules are defined by the US this seems to be OK provided it serves US interests,” Russia’s deputy U.N. ambassador Dmitry Polyansky tweeted.

European Union High Representative Josep Borrell, in softer terms, delivered the same message in August saying the United States “cannot be considered to be a JCPOA participant state for the purposes of possible sanctions snapback foreseen by the resolution.”