U.S. military leaders and elected officials are grappling with a worsening diplomatic and security crisis in the Middle East.

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

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 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.

Muscat is scheduled to host the sixth round of indirect negotiations between Tehran and Washington on Sunday. Foreign Ministry spokesperson Esmaeil Baqaei said on Tuesday that the Islamic Republic and the United States will hold the newest round of talks in Muscat next Sunday, with Oman as the mediator.

US President Donald Trump told Israeli Prime Minister Benjamin Netanyahu to end the war in Gaza and stop talk of an attack on Iran, according to a source familiar with the conversation.