US President Donald Trumps said Monday that the United States was starting direct talks with Iran over its nuclear programme, during a meeting with Israeli Prime Minister Benjamin Netanyahu.

"We know that certain contacts -- direct and indirect -- are planned in Oman. And, of course, this can only be welcomed because it can lead to de-escalation of tensions around Iran," Kremlin spokesman Dmitry Peskov said.

Russia "absolutely" supported the diplomatic initiative, he added.

Moscow had previously called for tensions between Washington and Tehran to be resolved diplomatically, following Trump's apparent threat to bomb Iran if it did not come to the negotiating table.

Expert-level consultations between Russia, China and Iran on nuclear issues were also set to take place in Moscow on Tuesday, the Russian foreign ministry said.

China urged the United States to show "sincerity" in the talks with Iran, which confirmed the negotiations set to take place in Oman, but stressed they were "indirect" talks.

The Iranian nuclear deal collapsed after Washington abandoned it in 2018 during Trump's first term and reimposed sweeping sanctions.

Trump's announcement came after Iran dismissed direct negotiations on a new deal to curb the country's nuclear programme and called the idea pointless.

The Russian parliament also on Tuesday voted to ratify a comprehensive strategic partnership treaty with its ally Iran.

With Russia facing sanctions over its military offensive in Ukraine, Moscow and Tehran have stepped up their cooperation in recent years.