DUBAI, United Arab Emirates — The United States on Wednesday accused Iran of ‘‘nuclear extortion’’ and said its plans to ramp up its atomic energy activities would ‘‘exacerbate’’ tensions and isolate Tehran.

‘‘There is no credible reason for Iran to expand its nuclear program, and there is no way to read this as anything other than a crude and transparent attempt to extort payments from the international community,’’ the United States said at an emergency meeting of the International Atomic Energy Agency, which monitors Iran’s nuclear activities.

Iran this week began enriching uranium beyond the limit set under its 2015 agreement with world powers, which curbed its atomic energy activities in exchange for widespread sanctions relief.


In its statement to the IAEA board of governors, the United States called on Tehran to pursue negotiations ‘‘without preconditions.’’

‘‘Iran should also know, however, that the only path to sanctions relief is through such negotiations, not nuclear extortion,’’ it said.

President Trump threatened Iran with more sanctions Wednesday and said on Twitter — without citing any evidence — that Iran ‘‘has long been secretly ‘enriching’” uranium in violation of the deal.

The remarks come amid high-level efforts to salvage the 2015 nuclear pact, also known as the JCPOA. Trump abandoned the agreement last year and reimposed a near-total embargo on the Iranian economy.

At the IAEA headquarters in Vienna, Russia’s mission called the emergency session — which was requested by the United States — extraordinary and said Iran’s low-enriched uranium ‘‘does not create risks in terms of proliferation of nuclear weapons.’’

‘‘The root cause of [Iran’s] countermeasures are obvious to us. The terms of the deal were violated long ago,’’ Russia said of the US decision to withdraw. ‘‘And it was not Iran who did this.’’

European nations, including France, Germany, and Britain, said in a joint statement that they were ‘‘deeply concerned that Iran is pursuing activities inconsistent with its JCPOA commitments.’’


They urged Iran to ‘‘immediately reverse the actions and to avoid any further escalatory steps.’’

But the head of Iran’s Supreme National Security Council, Ali Shamkhani, said Wednesday that Iran would not reverse its decision to boost uranium enrichment, characterizing it as an ‘‘unchangeable strategy’’ to compel world powers to reset the terms of the pact.

He spoke during a meeting with French presidential envoy Emmanuel Bonne, who was in Tehran to help ease tensions.

Shamkhani accused Europe of failing to guarantee Iran the economic benefits promised under the deal.

‘‘Iran’s step-by-step reduction of its nuclear commitments is an unchangeable strategy and that will continue . . . until Iran’s demands are fully met,’’ he said, the state-run Islamic Republic News Agency reported.

Earlier this month, Iran also breached the 300-kilogram limit on the amount of enriched uranium allowed under the agreement and warned that it would continue to scale back its obligations at 60-day intervals. European nations have urged Iran to reverse course and comply with the pact.

But Iranian officials, including President Hassan Rouhani, have criticized Europe for what they say is a policy of censuring Iran while allowing US violations of the deal to go unpunished.

‘‘On one side, Americans described the JCPOA as the worst possible deal and withdrew from it,’’ Rouhani said at a cabinet meeting Wednesday, according to the Mehr news agency. ‘‘On the other side, when Iran reduces its commitments to the deal, everyone expresses concern, while they should be concerned about the United States, which violated the entire agreement.’’


He said the US request to convene the IAEA’s board of governors was ridiculous.