Foreign Minister Abbas Araghchi said Iran's principal aim remained the lifting of sweeping US sanctions. Their reimposition by President Donald Trump in 2018 has dealt a heavy blow to the Iranian economy.

Trump made the surprise announcement that his administration would open talks with Iran during a White House meeting on Monday with Israeli Prime Minister Benjamin Netanyahu, whose country is an arch foe of Tehran.

Trump said the talks would be "direct" but Araghchi insisted his negotiations with US Middle East envoy Steve Witkoff on Saturday would be "indirect".

"We will not accept any other form of negotiation," Araghchi told official media. "The format of the negotiations... is not the most important thing in my view. What really counts is the effectiveness or otherwise of the talks.

"If the other side shows enough of the necessary willingess, a deal can be found... The ball is in America's court."

Speaking Monday in the Oval Office, Trump said he was hopeful of reaching a deal with Tehran, but warned that the Islamic republic would be in "great danger" if the talks failed.

"We're dealing with the Iranians, we have a very big meeting on Saturday and we're dealing with them directly," Trump told reporters.

Trump's announcement came after Iran dismissed direct negotiations on a new deal to curb the country's nuclear activities, calling the idea pointless.

The US president pulled out of the last deal in 2018, during his first presidency, and there has been widespread speculation that Israel, possibly with US help, might attack Iranian facilities if no new agreement is reached.

- 'Great danger' -

Trump issued a stern warning to Tehran, however.

"I think if the talks aren't successful with Iran, I think Iran's going to be in great danger, and I hate to say it, great danger, because they can't have a nuclear weapon," he said.

In an interview with US network NBC late last month. Trump went further. "If they don't make a deal, there will be bombing," he said.

China and Russia held consultations with Iran in Moscow on Tuesday, after which the Kremlin welcomed the planned talks.

Key Iranian ally Russia welcomed the prospect of negotiations for a new nuclear accord to replace the deal with major powers that was unilaterally abandoned by Trump in 2018.

"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, adding that Moscow "absolutely" supported the initiative.

China called on the United States to "stop its wrong practice of using force to exert extreme pressure" after Trump threatened Iran with bombing if it fails to agree a deal.

"As the country that unilaterally withdrew from the comprehensive agreement on the Iran nuclear issue and caused the current situation, the United States should demonstrate political sincerity (and)... mutual respect," its foreign ministry spokesman Lin Jian said.

Washington should "participate in dialogue and consultation, and at the same time stop its wrong practice of using force to exert extreme pressure", Lin added.

The Israeli prime minister, whose government has also threatened military action against Iran to prevent it developing a nuclear weapon, held talks with Witkoff as well as Trump on Monday.

Netanyahu was a bitter opponent of the 2015 agreement between Iran and Britain, China, France, Germany, Russia and the United States which Trump later abandoned.

That deal saw Iran receive relief from international sanctions in return for restrictions on its nuclear activities overseen by the UN watchdog, the International Atomic Energy Agency.

Trump's withdrawal from the deal was followed by an Iranian decision one year later to stop complying with its own obligations under the deal.

The result has been that Iran has built up large stocks of highly enriched uranium that leave it a short step from weapons grade.

In its latest quarterly report in February, the IAEA said Iran had an estimated 274.8 kilograms (605 pounds) of uranium enriched to up to 60 percent. Weapons grade is around 90 percent.

buts/kir/ami