Iran’s supreme leader has criticized an initial proposal from the United States in negotiations over Tehran’s rapidly advancing nuclear program.

Alarmed by an intelligence assessment that Iran will be able to produce nuclear weapons within months if not weeks, Israel has launched a massive air campaign aiming to destroy the country’s nuclear program.

The two sides were scheduled to meet for a sixth round of negotiations on Sunday. Oman, which was set to host the talks, said on Saturday that this round had been canceled.

"I am pleased to confirm the 6th round of Iran US talks will be held in Muscat this Sunday the 15th," Bad Albusaidi, the country's foreign minister said on social media.

Iran’s supreme leader has denounced a proposal by the United States aimed at curbing Tehran’s nuclear efforts and demanded that his country retains national independence amid reports of Washington offering to become involved in Tehran’s nuclear program.

Iran and the United States on June 9 indicated that talks on Iran’s nuclear program will continue but the two side gave different dates for the next round of Iran-US indirect negotiations.

Iran's stance directly clashes with U.S. President Donald Trump 's position that Iran must halt all enrichment amid negotiations marked by uncertainty, despite having reached their most significant step since they began in April with a U.S. offer being delivered to Tehran last week.

Iran warns it will strike all US bases in the region if nuclear talks fail, as tensions rise over missiles and uranium enrichment ahead of the next negotiation round in Oman.