Trump threatened to "obliterate" Iran's power plants if it did not reopen the strategic waterway within 48 hours, which were due to end late Monday.

The waterway has remained effectively closed since the start of the war sparked on February 28 by US-Israeli bombardment of Iran.

"We believe that the situation should have transitioned to a political and diplomatic settlement," Kremlin spokesman Dmitry Peskov told journalists, including from AFP, at a briefing.

"This is the only thing that can effectively contribute to defusing the catastrophically tense situation that has now developed in the region," Peskov said.

Russia -- which helped build Iran's only operational nuclear power plant at Bushehr -- has warned against strikes that could endanger the site that the UN's nuclear watchdog announced last week was hit by a projectile.

"Of course, this poses a very serious security threat if this trend continues," Peskov said Monday.

"We consider strikes on nuclear facilities to be potentially extremely dangerous and fraught with, perhaps even irreversible, consequences," he added.

Russia was in "constant dialogue" with the International Atomic Energy Agency (IAEA) on the Bushehr plant, Peskov said.

Agency head Rafael Grossi called "for restraint during the conflict to avoid any risk of a nuclear accident", the IAEA said in a statement last week.