Talks between Iran and the United States over Tehran’s rapidly advancing nuclear program are “in a very crucial” stage.

But Iran’s foreign minister said Tehran planned to participate “calmly and coolly” in the negotiations. Both sides will meet in Rome on Saturday for a second round, Iran’s Foreign Ministry said.

The UN nuclear watchdog should play a role in nuclear talks between Tehran and Washington, International Atomic Energy Agency chief Rafael Grossi said on Thursday, ahead of a second round of talks between the U.