In a letter to the 15-member body on Friday, the three European parties to the nuclear deal, officially known as the JCPOA, said any decision or action taken to reimpose UN sanctions "would be incapable of legal effect”, Reuters reported.
The United States quit the nuclear deal in 2018.
"We have worked tirelessly to preserve the nuclear agreement and remain committed to do so," said the UN envoys for Britain, France and Germany, adding that they remain committed to "fully implementing" a 2015 Security Council resolution that enshrines the pact, which also included Russia and China.
US Secretary of State Mike Pompeo said last month that he triggered a 30-day process at the Security Council leading to a return of UN sanctions on Iran on Saturday (0000 GMT Sunday) that would also prevent a conventional arms embargo on Tehran from expiring on Oct. 18.
But 13 of the Security Council members say Washington's move is void because it is no longer a party to the nuclear deal. The United States say it can make the move because the 2015 Security Council resolution still names it as a participant.
US President Donald Trump plans to issue an executive order in the coming days allowing him to impose US sanctions on anyone who violates the UN arms embargo on Iran, sources said on Thursday, in a bid to reinforce the US assertion that the measure has been extended indefinitely beyond Oct. 18.