Secretary of State Mike Pompeo on Thursday began the process to “snapback” U.N. sanctions on Iran, promising that “America will not appease” and taking aim at European allies who he accused of endangering their people.

“Our message is very, very simple, the United States will never allow the world's largest state sponsor of terrorism to freely buy and sell planes tanks missiles and other kinds of conventional weapons,” he said at a press conference outside the U.N. Security Council.

TRUMP ADMINISTRATION TO TRIGGER 'SNAPBACK' OF UN SANCTIONS ON IRAN: WHAT DOES IT MEAN?

The U.S. triggered the “snapback” mechanism nearly a week after an effort by the U.S. to extend a soon-to-expire arms embargo on Iran failed at the U.N. Security Council after allies on the Council abstained.

“America will not join in this failure of leadership,” Pompeo said. “America will not appease, America will lead.”

Pompeo noted that in addition to the embargo, snapback would also reimpose sanctions on ballistic missile testing and ongoing nuclear activity, threats he said had been “foolishly downplayed” by the authors of the Obama-era deal to limit Iran's nuclear program.

He also took direct aim at the United Kingdom, France and Germany for not supporting the extension, while accusing them of privately telling him they didn’t want the embargo lifted.

“And yet today, in the end, they provided no alternatives, no options. No country but the United States has had the courage and conviction to put forward a resolution,” he said. “Instead they chose to side with the ayatollahs. Their actions endangered the people of Iraq, of Yemen, of Lebanon, of Syria and indeed their own citizens as well.”

The U.S. left the Iran nuclear deal in 2018, but officials claim to retain rights as a participant of the accompanying U.N. Security Council Resolution 2231, which allows individual participants to trigger the “snapback” process if they decide Iran is not in compliance with the deal.

TRUMP SAYS US INTENDS TO TRIGGER 'SNAPBACK' OF UN SANCTIONS ON IRAN 

Pompeo informed the president of the U.N. Security Council of the U.S. intention, triggered a 30-day countdown to the re-imposition of almost all sanctions, including the arms embargo. It can be stopped if the Council passes a resolution to extend sanctions relief, but that would almost certainly be vetoed by the U.S.

However, European countries, as well as Russia and China have indicated they could ignore the U.S. “snapback,” citing the U.S. departure from the agreement as a move that makes snapback illicit. The Trump administration has not ruled out sanctioning countries that do not comply with those restrictions.

“Our position regarding the effectiveness of the U.S. notification pursuant to resolution 2231 has consequently been very clearly expressed to the presidency and all UNSC Members,” Germany, France and the U.K. said in a statement referring to the Security Council. “We cannot, therefore, support this action, which is incompatible with our current efforts to support the" nuclear deal.

The countries' representatives said they remain committed to the Joint Comprehensive Plan of Action, the formal name for the Iran nuclear deal. Iranian non-compliance with the obligations spelled out in the deal should be addressed through dialogue and processes spelled out in the agreement.

The Iranian ambassador to the U.N., meanwhile, described the U.S. letter as “null and void and [having] no legal standing and is thus inadmissible.”

Russia and China have also objected to the move, with Russia calling for a meeting of Security Council leaders to come to an alternative arrangement.

Meanwhile, Pompeo noted that a number of Persina Gulf nations, including Bahrain, Kuwait, the United Arab Emirates and Saudi Arabia, had called for the arms embargo to be extended.

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“As Iran’s neighbors, they know more than anyone the havoc Iran could create with those weapons,” he said.

Iranian dissidents too, welcomed the move, saying it would help in their efforts to oust the theocratic regime in Tehran.

“Reimposing the prior [Security Couoncil] sanctions on the ruling mullahs in Iran, helps the Iranian people in their quest to liberate their country because sanctions would weaken the Supreme Leader and the [Iran Revolutionary Guard Corps] who are responsible for suppressing dissent and killing freedom-seeking protesters,” Alireza Jafarzadeh, deputy director of the National Council of Resistance of Iran'sWashington office, said in a statement.

Fox News’ Ben Evansky and Rich Edson contributed to this report.