That would be far above the 3.67 percent limit Iran had accepted under the 2015 nuclear deal with world powers, but still short of the around 90 percent required to make an atomic bomb.

Iran has repeatedly denied that it is seeking to build nuclear weapons, a point Khamenei reiterated in the comments that were posted on his official website Monday.

His remarks came at a time Tehran, US President Joe Biden and European powers are trying to salvage the troubled nuclear accord.

The deal has been on the brink of collapse since former US president Donald Trump unilaterally withdrew his country in 2018, reimposing crippling sanctions on Iran.

Tehran responded a year later by gradually scaling back most of its key commitments.

In early January, it boosted uranium enrichment back to 20 percent, the level it had reached before the landmark deal.

Khamenei said that "Iran's enrichment limit will not be 20 percent, and we will act to the point that is needed and the country requires".

He added that "we could bring enrichment to 60 percent" for nuclear propellants and other purposes.

"The Islamic republic will not back down on the nuclear issue and will strongly continue down the path of what the country requires for today and tomorrow."

- 'Still reversible' -

The 2015 nuclear deal limited Iran's enrichment to 3.67 percent, among other restrictions, in exchange for international sanctions relief.

Khamenei stressed that it was the United States that left the deal and emphasised that Iran's suspended commitments can be reversed.

"Our respected government did not abandon its commitments and gradually reduced some of them, which are still reversible in the case that they return to their responsibilities," he said.

Biden has signalled a readiness to revive the deal but insists Iran first return to all its nuclear commitments, while Tehran demands Washington take the first step by scrapping the sanctions.

In an apparent comment on Israel's Prime Minister Benjamin Netanyahu, whose country Iran blames for sabotage attacks on its nuclear programme, Khamenei said: "That clown of the Zionist regime keeps saying that we won't let Iran have nuclear weapons."

He said that "if the Islamic republic had meant to gain nuclear weapons, he (Netanyahu) and those mightier than him could not stop it", but also insisted that "Islamic thought and principles" prevent Iran from seeking weapons of mass destruction.

In the standoff, Iran's parliament late last year demanded that Tehran limit some inspections by the International Atomic Energy Agency (IAEA) if sanctions were not lifted by a Sunday deadline, a step that will go into force on Tuesday.