United Nations nuclear watchdog chief Rafael Grossi said Thursday that Iran and the United States were running out of time to secure a deal ahead of a fresh round of nuclear talks between Tehran and Washington.

"We are in a very crucial stage of these important negotiations. We know we don't have much time, this is why I am here... to facilitate this process," Grossi said during a joint press conference in Tehran with the head of Iran's atomic energy agency, Mohammad Eslami.

France's President Emmanuel Macron, U.S. Secretary of State Marco Rubio and U.S. envoy Steve Witkoff in Paris Thursday began a meeting on crafting a Ukraine ceasefire, an AFP photographer said.

The lunch-time meeting at the French presidential palace comes as Ukraine and its European allies seek to pressure Russia into agreeing to a deal, days after Witkoff again met Russian President Vladimir Putin.

U.S. Secretary of State Marco Rubio is headed Wednesday to Paris for talks on ending the war in Ukraine, his office said.

The State Department said in a communique that Rubio is traveling with U.S. envoy Steve Witkoff for talks with European officials on advancing President Donald Trump's goal of ending the war triggered by the Russian invasion of its pro-Western neighbor in 2022.

Iranian Foreign Minister Abbas Araghchi will visit Moscow on Thursday for talks, Iran's envoy to Russia said Wednesday, after Washington and Tehran held indirect talks over Iran's nuclear program last week.

"Dr Araghchi will arrive in Moscow tomorrow on a visit to hold consultations with Russian top officials," Iran's ambassador to Russia Kazem Jalali wrote on X.

Iranian President Masoud Pezeshkian said Wednesday he hopes a deal can be reached with the United States, as the two countries prepare for a second round of nuclear talks this weekend.

"We would naturally welcome the conclusion of an agreement" with the U.S., Iran's official IRNA news agency quoted Pezeshkian as saying during a cabinet meeting.

Foreign Minister Abbas Araghchi said Wednesday that Iran's enrichment of uranium as part of its nuclear program was "non-negotiable" after US Special Envoy Steve Witkoff called for a halt.

Iran's supreme leader Ayatollah Ali Khamenei on Tuesday voiced satisfaction with recent talks with the United States, expressing confidence in the Islamic Republic's position but casting doubt on U.S. intentions.

The talks were "well carried out in the first steps. Of course, we are very pessimistic about the other side, but we are optimistic about our own capabilities," state TV quoted Khamenei as saying.

A second U.S. aircraft carrier is operating in Mideast waters ahead of the next round of talks between Iran and the United States over Tehran's rapidly advancing nuclear program, satellite photos analyzed Tuesday by The Associated Press showed.

The operation of the USS Carl Vinson and its strike group in the Arabian Sea comes as suspected U.S. airstrikes pounded parts of Yemen controlled by the Iranian-backed Houthi rebels overnight into Tuesday. American officials repeatedly have linked the U.S.' monthlong campaign against the Houthis under President Donald Trump as a means to pressure Iran in the negotiations.

Talks between Iran and the United States over Tehran's rapidly advancing nuclear program appeared ready to leave the Middle East on Monday, as an Italian source and others said the next round of negotiations would take place in Rome. But early Tuesday, Iran insisted the next round would again be held in Oman.

It wasn't immediately clear where the negotiations would be held after Tehran's overnight announcement. American officials have not said where the talks would be held. President Donald Trump separately complained Monday about the pace of nuclear talks between the United States and Iran as the two countries start a new round of pivotal negotiations.

Iran's Islamic Revolutionary Guard Corps said Tuesday the country's military capabilities were off limits, ahead of a second round of talks with the United States on its nuclear program.

"National security and defense and military power are among the red lines of the Islamic Republic of Iran, which cannot be discussed or negotiated under any circumstances," Guards spokesman Ali Mohammad Naini said, quoted by state broadcaster IRIB.