U.S. and Iran agree to Friday talks in Oman – Reuters

The U.S. and Iran have agreed to hold talks in Oman on Friday, Reuters reported citing officials from both sides, amid heightened tensions as the U.S. builds up forces in the Middle East and regional players seek to avoid a military confrontation that many fear could escalate into a wider war.

Asked on Wednesday whether Iran's Supreme Leader Ayatollah Ali Khamenei should be worried, Trump told NBC News: "I would say he should be very worried. Yeah, he should be." He added that "they're negotiating with us" but did not elaborate.

After Trump spoke, U.S. and Iranian officials said the two sides had agreed to shift the talks' location to Muscat after initially accepting Istanbul, according to Reuters.

But there was no indication they had found common ground on the agenda.

Iran has pushed to restrict the negotiations to discussing its long-running nuclear dispute with Western countries.

But U.S. Secretary of State Marco Rubio presented a different view on Wednesday. "If the Iranians want to meet, we're ready," Reuters quoted Rubio as saying at a press briefing. But he added that talks would have to include the range of Iran's ballistic missiles, its support for armed proxy groups around the Middle East and its treatment of its own people, besides nuclear issues.

A senior Iranian official said, however, that Iran's missile programme was "off the table." A second senior Iranian official said Tehran would welcome negotiations over the nuclear dispute but that U.S. insistence on dealing with non-nuclear issues could jeopardize the talks, according to Reuters.