Zarif's visit came as Tehran said it had stopped respecting limits on its nuclear activities agreed under the deal until other signatories find a way to bypass renewed US sanctions.

Lavrov said during a joint press conference that the 2015 agreement had been "fragile" since US President Donald Trump announced Washington would pull out a year ago.

European signatories of the deal, known as the Joint Comprehensive Plan of Action (JCPOA), were trying to "divert attention" from their inability to implement points of the agreement, Lavrov said.

"We will call on them, as we have done before, to concentrate on implementing everything that is enshrined in the JCPOA and approved by the UN Security Council."

Lavrov said European mechanisms to allow banking transactions with Iran despite US sanctions were inefficient.

"For Iran, it is important that this mechanism allows for the export of Iranian oil. We support the Iranians. This is a legal requirement and part of the JCPOA."

Zarif meanwhile said "our friends in Russia and China maintained very good relations with us in this year," since the US withdrawal.

"But the rest of the JCPOA participants did not meet any of their obligations," he said, referring to Britain, France and Germany.

"Yes, they issued good statements, but in practice nothing happened."

Lavrov also criticised Washington for sending aircraft carriers to the Persian Gulf, "suggesting a willingness to use force".

Washington reimposed sanctions after it quit the agreement one year ago, dealing a severe blow to the Iranian economy.