The United States informed Iran on Wednesday that it would not accept Tehran’s attempts to change the location or structure of talks set for Friday, according to a U.S. official familiar with the discussions.

"We told them it is this or nothing, and they said, 'Ok, then nothing'," the Axios website quoted an unnamed senior U.S. official as saying.

The report came after Iranian media said the indirect talks between Iran and the U.S. are set to take place on Friday in Oman’s capital Muscat, with discussions expected to focus on Tehran’s nuclear program and the lifting of sanctions.

The nuclear talks between the two countries were originally scheduled to take place in Istanbul, Türkiye.

Per Axios, the official said that if the Iranians are willing to go back to the original format, the U.S. is ready to meet this week or next week.

"We want to reach a real deal quickly or people will look at other options," the senior official said.

Differences over the scope of the talks and lack of agreement on a venue raised doubts whether the meeting would take place as planned, leaving open the possibility that U.S. President Donald Trump could carry out his threat to strike Iran.

"If the Iranians want to meet, we're ‌ready," Rubio said. But he added that talks would have to include the range of Iran's ballistic missiles, its support for groups ‍around the Middle East and its treatment of its own people, besides the nuclear dispute.

A senior Iranian official, however, said the talks would only be about Iran's nuclear programme, and that its missile programme was "off the table." A second senior Iranian official said U.S. insistence on discussing non-nuclear issues could jeopardize the talks that Tehran wants to hold in Oman.