"We note recurring signals from Washington in favor of the so-called improvements of the existing agreement and possible supplements to it," Ryabkov told the Tass news agency on Sunday commenting on US State Secretary Rex Tillerson’s statement on possible amendments or a secondary agreement on the Iranian nuclear program.
"What is to be improved in this context is the implementation of the existing agreements by the US side,” he added.
"There is an American saying our overseas colleagues often use in such situations: ‘If it’s not broke, don’t fix it,’" Ryabkov said.
"That’s what I would like to address to the colleagues in the United States."
Russia plans to stress in its contacts with Iran in the near future that it is important to keep the nuclear deal intact, the senior diplomat said.
"Naturally, in our contacts with Iranian colleagues we will stress the importance of keeping the Joint Comprehensive Plan of Action (JCPOA) as it was reached and the importance of it being completely implemented," he said.
"I am not ready to provide concrete names or dates but, obviously, we will discuss these topics in the near future."
Earlier on Sunday, US Secretary of State Rex Tillerson said that Washington would continue to cooperate with partners under the Joint Comprehensive Plan of Action (JCPOA), which is geared to settle the crisis around Iran’s nuclear program, seeking to reach a secondary agreement to address other concerns.
Speaking from the White House on Friday, Trump said he would not recertify that Tehran is complying with the nuclear agreement.
Federica Mogherini, the foreign policy chief of the European Union, who was one of the key participants of the nuclear talks in 2015, denounced Trump's decision in decertifying Iran's deal.
“A nuclear agreement which is working well cannot be dismantled,” she said.