Russia's top diplomat has denounced the pullout by the US of the 2015 Iran nuclear deal as a “significant” violation of a United Nations resolution that endorsed the international document back then.

During a Thursday press conference with his visiting German counterpart, Heiko Maas, Russian Foreign Minister Sergei Lavrov said Washington cannot unilaterally reinstate those anti-Iran sanctions, which were lifted by the United Nations.

“We are seriously concerned about the decision of the US administration to withdraw from the Joint Comprehensive Plan of Action (JCPOA), thereby committing a significant violation of Security Council resolution 2231,” Lavrov said, referring to the deal by its official name.

Resolution 2231 was adopted by the UN Security Council in July 2015 to endorse the landmark nuclear agreement, which had been concluded days earlier between Iran, on the one side, and the 15-nation body’s permanent members plus Germany, on the other.

American President Donald Trump sparked widespread international criticisms late on Tuesday, when he announced Washington was walking away from the Iran deal.

The US president also said the “highest level” of economic sanctions would be reinstated against Iran, threatening similar bans against any nation that helped Iran in what he claimed to be “its quest for nuclear weapons.”

Washington’s five other partners in the deal took turns to censure Trump’s attack on the multilateral Iran deal, vowing that they would stick to their commitments under the accord despite the US withdrawal.

The European Union, which moderated the discussions in the run-up to the deal, also came out in support of the deal, warning the White House against any attempt to harm the European firms doing business with Iran.

The Russian foreign minister further censured Washington’s withdrawal from the JCPOA as a “very, very significant blow” to the nuclear non-proliferation regime in the region, warning that it was unreasonable to ignore the interests of Tehran and its partners.

“Speaking of the US unilateral sanctions, we could not do anything about it. However, it does not apply to the lifting of the UNSC sanctions as this decision could not be revisited,” Lavrov said.

Lavrov, meanwhile, praised Iran’s “balanced reaction” to Trump’s move, adding that in this situation “the haste would probably be unproductive.”

The remaining signatories, he added, are working to find ways to preserve the Iran deal,

Iran has said it will remain in the JCPOA for now, pending negotiations with the other signatories in the coming weeks before making a final decision on its future role in the pact. Tehran had earlier warned that it has prepared several options for responding to US withdrawal.

Berlin wants Iran deal to stay

For his part, the German foreign minister emphasized the importance of protecting the Iran deal.

Russian Foreign Minister Sergei Lavrov (R) shakes hands with his German counterpart, Heiko Maas, during a joint press conference following their talks in Moscow on May 10, 2018. (Photo by AFP)

“It is very important to ensure the compliance with this agreement. It is of vital importance for us and for our partners in France and the United Kingdom that Iran continues to fully comply with the existing restrictions and commitments, that Iran remains a party to the agreement,” Maas said.

US breaching WTO rules

Earlier in the day, Russia’s Deputy Foreign Minister Sergei Ryabkov reaffirmed Moscow’s support for Iran.

Ryabkov was cited by Russian media as saying that Moscow was firmly committed to continuing to deepen ties with Tehran despite Washington’s decision to quit the deal.

Meanwhile, Kremlin spokesman, Dmitry Peskov, said Trump’s move to reinstate unilateral sanctions against Iran and companies doing trade with Tehran contained hidden protectionism and violated the regulations of the World Trade Organization (WTO).

"In fact, we are talking about veiled protectionism, and we are talking about steps that are certainly absolutely contrary to the norms and rules of the World Trade Organization,” he said.

On Wednesday, the EU also threatened to take the US to the WTO if it took any steps against European businesses in Iran.

A spokesman for the French government said EU partners would discuss the economic fallout from the US decision.

“The European Union is ready to challenge at the WTO any unilateral measure that would hurt the interests of European companies and respond in a proportionate manner, in accordance of course with the rules of that international organisation,” Benjamin Griveaux said.