Iranian Foreign Minister Mohammad Javad Zarif who arrived in Chinese capital city of Beijing early on Sunday left China for Russian capital city of Moscow after holding a meeting with his city counterpart on the JCPOA.
Under the deal signed in Vienna with six world powers - China, France, Russia, the United Kingdom, the US, Germany, and the European Union - Iran scaled back its uranium enrichment programme and promised not to pursue nuclear weapons in exchange for the lifting of economic sanctions. On May 13, he visited China, and after the talks with Lavrov he will travel to Brussels where he will meet with EU Foreign Policy Chief Federica Mogherini and top German, French and British diplomats.
US President Donald Trump said the deal was "horrible" because of expiry dates on its restrictions and because it did not cover Iran's ballistic missile programme or its regional influence.
Before leaving, Zarif published a government statement on his Twitter page, slamming Trump's "extremist administration" for abandoning "an accord recognised as a victory of diplomacy by the worldwide community".
Media captionWhat is the Iran nuclear deal?
Lavrov and Zarif have other issues to discuss as well, primarily the situation in Syria, which deteriorated in the wake of Washington's decision to withdraw from the JCPOA.
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"We are waiting now for how the decision-makers in the European Union will react". Iran wants the Europeans and others to give it clear-cut guarantees about fulfilling their obligations if Tehran remains in the deal.
Iran denies that version of events, saying the Israeli strikes were launched on "invented pretexts".
Meanwhile, European diplomats in Tehran fumed that Trump's decision to withdraw from the deal could undermine years of patient work to restore commercial and diplomatic ties with the Islamic Republic.
"China and Iran have comprehensive strategic partnership and are trade partners and these relations still continue", he noted.
The 2015 agreement "is delivering on its goal, which is guaranteeing that Iran doesn't develop nuclear weapons, the European Union is determined to preserve it", Mogherini said, warning that she was "particularly worried" by the US announcement of fresh sanctions.