"The foreign minister's political deputy Abbas Araghchi has in a letter to (the International Atomic Energy Agency) announced that Iran will start 60 percent enrichment," IRNA news agency said, without specifying when.

Such a move would bring Iran closer to the 90 percent threshold for military use in a new breach of commitments it has made to the international community.

Iran is allowed to enrich uranium up to a maximum of 3.67 percent under the terms of a nuclear agreement it reached with world powers in 2015.

It has been enriching uranium up to 20 percent purity since January.

IRNA said Iran would also add "1,000 centrifuges with 50 percent more capacity to the machines present in Natanz, in addition to replacing" those damaged in Sunday's attack on the nuclear facility.

According to Iran's English-language channel Press TV, the enrichment jump would start on Wednesday.

Iran has accused its arch enemy Israel of sabotaging the Natanz uranium enrichment plant and vowed it would take "revenge" and expand its nuclear activities.

The "sabotage occurred in a duct of power cables leading to the centrifuge machines which caused damage to this system," said government spokesman Ali Rabiei.

"This was not an external attack and the location of the sabotage has been clearly determined," he added.

Tehran's announcement comes hours after a visit by Russia's Foreign Minister Sergei Lavrov, during which Tehran and Moscow presented a united front against the West ahead of ongoing nuclear negotiations at Vienna.

Talks in the Austrian capital are focused on bringing the United States back into the troubled accord after it withdrew in 2018 under then US president Donald Trump.

Iran retaliated as of 2019 by gradually dropping most of its major commitments under the deal.

Araghchi, who heads Iran's delegation, left Tehran for Vienna at midday on Tuesday.