"Under our potential Agreement -- WE WILL NOT ALLOW ANY ENRICHMENT OF URANIUM!" Trump said on his Truth Social network, after the Axios news outlet said Washington's offer would let Tehran enrich some of the nuclear fuel.

Republican Trump also blamed predecessor Joe Biden for the current situation, saying that the Democrat "should have stopped Iran a long time ago from 'enriching.'"

Iran has held five rounds of talks with the United States since April in search of a new agreement to replace the deal with major powers that Trump abandoned during his first term in 2018.

Uranium enrichment has remained a key point of contention in the talks, with Iran defending what it says is its pursuit of a civil nuclear program but with the US side calling it a "red line".

Axios said the latest proposal that Washington had sent Tehran on Saturday would allow limited low-level uranium enrichment on Iranian soil, for an amount of time that has yet to be determined.

Key US ally Israel has repeatedly threatened military action against Iran's nuclear program.

But Trump said last week he had told Israeli Prime Minister Benjamin Netanyahu to hold off from striking Iran while the talks continue.