Russian Foreign Minister Sergey Lavrov and the Chinese government’s top diplomat, Wang Yi, both wrote to the 15-member council and UN chief Antonio Guterres as the United States threatens to spark a so-called sanctions snapback under the Iran nuclear deal, even though Washington quit the accord in 2018.

In a letter to UN Secretary-General Antonio Guterres and the Security Council circulated Monday, the Russian minister said statements by US State Department officials that the Trump administration doesn’t plan to resume its commitments under the nuclear deal but plans to invoke rights allegedly deriving from the resolution endorsing it are “ridiculous and irresponsible,” according to the Associated Press.

He said the United States withdrew from the 2015 nuclear agreement between Iran and six major powers and now has no legal right to try to use the UN resolution endorsing the deal to indefinitely continue the arms embargo, which is set to expire on Oct. 18.

Lavrov’s letter went further in explaining Moscow’s strong opposition to an indefinite arms embargo and US use of the “snap back” provision.

“We are proceeding on the basis that the United Nations should not become hostage to the political situation in the United States, which has decided to withdraw from the plan,” he said. “There are no valid grounds for raising in the Security Council the issue of an arms embargo against Iran.”

Washington has threatened to trigger a return of UN sanctions on Iran if the Security Council does not extend an arms embargo due to expire in October under Tehran’s deal with world powers to prevent it from developing nuclear weapons.

US Ambassador to the UN Kelly Craft said last week that a draft resolution on the embargo would be circulated soon.

Council veto-powers Russia and China have already signaled they are against reimposing an arms embargo on Iran. If they block the US-drafted resolution, then Washington will have to follow through on its sanctions snapback threat.

“The United States, no longer a participant to the JCPOA (nuclear deal) after walking away from it, has no right to demand the Security Council invoke a snapback,” Wang wrote in his June 7 letter.

The 2015 Iran nuclear deal, enshrined in a UN resolution, allows for the return of sanctions on Iran, including the arms embargo, if Iran violates the deal. US President Donald Trump quit the deal in 2018, branding the accord from Barack Obama’s presidency as “the worst deal ever.”

The United States claims it can still trigger the sanctions snapback because the 2015 UN resolution still names it as a participant. Diplomats say Washington would likely face a tough, messy battle.

EU Foreign Policy Chief Josep Borrell has also reacted to US efforts to extend Iran’s arms embargo within the framework of JCPOA noting the US withdrew from the Nuclear Deal and cannot claim to be a member anymore.