Tehran's ambassador to Iraq will head the Iranian team's delegation for the landmark direct talks with the Unites States next week in Baghdad, a foreign ministry spokesman announced Friday.

Mohammad-Ali Hosseini, the spokesman, told the state IRNA news agency that Ambassador Hassan Kazemi was appointed to lead the Iranian delegation in the negotiations. "The Iran-US talks on Iraq will start on Monday, May 28," Hosseini said.

Although Kazemi had been cast as the likely chief Iranian in the talks, Hosseini's announcement was the first official statement on this.

The talks in Baghdad between U.S. and Iranian diplomats on efforts to stabilize Iraq will offer a very rare one-on-one forum between the two countries, which broke off formal relations after Iran's 1979 Islamic Revolution.

The agenda is expected to be limited to Iraqi affairs, without spilling over into the nuclear impasse between Iran and the West. However, that standoff is likely to hang over any interplay between Iran and the United States.

On Thursday, Iran's hard-line President Mahmoud Ahmadinejad vowed never to halt the country's controversial uranium enrichment program. His salvo followed a report by the U.N. nuclear watchdog that said Iran has expanded its enrichment in defiance of U.N. demands for a suspension. The finding could set the stage for a third round of Security Council sanctions.

U.S. President George W. Bush said Thursday he would work with allies to strengthen sanctions on Iran and criticized Iran's leaders who "continue to be defiant as to the demands of the free world."

U.S.-Iranian tensions have increased, despite the groundbreaking diplomatic overture. The Pentagon has moved two aircraft carriers and seven other ships into the Persian Gulf in a show of force. Iran, meanwhile, has detained at least two prominent American-Iranian citizens.

Monday's talks will also take place against the backdrop of five Iranians held by U.S. troops for more than three months after their January capture in the northern Iraqi city of Irbil.

U.S. authorities said the five were members of Iran's elite Quds Force, accused of arming and training Iraqi militants. Tehran has claimed they were part of a government liaison office and has demanded their release.

Kazemi last month said the continued incarceration of the five was having a negative effect on Iraq's sovereignty.