A Shahab-3 surface-to-surface missile is seen on display next to a portrait of Iranian Supreme Leader Ayatollah Ali Khamenei, at a street exhibition set up by Iran's army and paramilitary Revolutionary Guard to celebrate "Defense Week" in Tehran, in a Sept. 26 2019, file photo. STR/AFP/Getty

France, Britain and Germany on Thursday triggered a mechanism to reimpose United Nations sanctions on Iran for failing to comply with commitments over its nuclear program.

The three countries notified the U.N. Security Council that they "believe Iran to be in significant non-performance of its commitments" under a 2015 nuclear deal and "hereby invoke the process known as the 'snapback' mechanism," which initiates a 30-day process for reimposing sanctions suspended a decade ago.

Since President Trump pulled the U.S. unilaterally out of the deal during his first term in office, Iran has steadily abandoned the commitments it agreed to under the 2015 nuclear agreement, which was brokered by then-President Barack Obama, along with the "E3" European countries and the European Union.

U.S. Secretary of State Marco Rubio said Thursday that Washington was still seeking direct talks with Iran on ending its nuclear program in the wake of the E3 triggering the so-called "snapback" mechanism to reimpose the U.N. sanctions.

Rubio welcomed the move, which has long been pushed by Mr. Trump, but said: "At the same time, the United States remains available for direct engagement with Iran — in furtherance of a peaceful, enduring resolution to the Iran nuclear issue."

"Snapback does not contradict our earnest readiness for diplomacy, it only enhances it," Rubio said in a statement, lauding "the leadership of our E3 allies in this effort."

"I urge Iranian leaders to take the immediate steps necessary to ensure that their nation will never obtain a nuclear weapon; to walk the path of peace; and to, by extension, advance prosperity for the Iranian people," Rubio said in a statement.

Mr. Trump in his second term has swung sharply in different directions on Iran, insisting he sought a negotiated settlement but then ordering U.S. airstrikes on nuclear sites in support of an Israeli military campaign.

Referring to the E3's decision, Iran's Foreign Minister Abbas Araghchi said Thursday that Tehran would "respond appropriately to this illegal and unjustified action by the three European countries, in order to protect and guarantee its national rights and interests."

His office said he had delivered that message in a phone call with his French, British and German counterparts, adding that he had called on the three countries to "appropriately correct this wrong decision in the coming days."

While Araghchi did not specify what retaliatory measures Iran might take, Tehran has previously warned that such a move could lead to the exclusion of the European powers from any future negotiations on Iran's nuclear program.

Speaking with CBS News' Imtiaz Tyab early this summer, Araghchi said he was doubtful that talks with the U.S. would resume quickly, but he said the "doors of diplomacy will never slam shut."

The move by the European trio took place just days after Iranian and European diplomats held talks in Geneva, the second since Israel's attack on Iran that started a 12-day war in June.

The E3 had been threatening in recent weeks to activate the so-called "snapback" mechanism, citing Iran's continued non-compliance with its commitments under the 2015 nuclear agreement.

That deal was torpedoed in 2018 when Mr. Trump unilaterally withdrew the U.S. from the agreement and slapped crippling sanctions on Iran.

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