Senior U.S. officials say that Britain, and not the United States, invited an Iranian team to visit Iraq. But they say the Bush administration did not oppose the gesture and believes Iran could play a helpful role in defusing tensions between the U.S.-led coalition and Iraqi Shiites.

Officials here acknowledge there have been recent exchanges with Iran over the violence in Iraq, and they say they are hopeful the Iranians will make clear that they do not endorse violence or confrontation by Iraqi Shiites, and support the central authority in Baghdad.

The comments follow a statement by Iranian Foreign Minister Kamal Kharrazi that the United States had sought Tehran's help in ending insurgent violence in Iraq, and a subsequent announcement that an Iranian diplomat had gone to Baghdad for talks with the U.S.-appointed Iraqi Governing Council and Iraqi religious figures.

A senior U.S. diplomat who spoke on condition of anonymity said Britain, not the United States, invited the Iranian team to Iraq. At the same time, he said the Bush administration did not object to the British move and is hopeful Iran can uses its considerable influence with Iraq's Shiite community to help calm the situation.

At a news briefing, State Department spokesman Richard Boucher said the United States has long been urging Iran to do what it can to stabilize the situation in Iraq. While declining to discuss specific messages or dates, he said the point has been made again "recently".

"We have made clear to Iran as we have made clear to others of Iraq's neighbors that they need to play a helpful role," he said. "They need to play a positive role to calm the situation and help Iraq achieve the goal of a stable transition on July 1st and help with the reconstruction of a stable, democratic and peaceful neighbor. We have been concerned about the role that Iran has been playing, and it's something we monitor very closely."

The Iranian foreign minister said the U.S.-Iranian exchanges had been made through Switzerland, which looks after U.S. interests in Iran in the absence of direct relations.

It is unclear whether the Iranian team in Iraq would meet with rebel Shiite cleric Moqtada al-Sadr, whose militia followers have battled coalition forces this month in Najaf and several other Iraqi towns.

Asked about a reported offer by Mr. al-Sadr to drop preconditions for peace talks, spokesman Boucher said the United States is "open and willing" to look for a peaceful resolution of the situation in the Najaf area.

But he said Mr. al-Sadr, who faces Iraqi charges in the killing of a rival cleric, needs to face justice, and his "Mahdi Army" militia should be disbanded along with other such groups.

Mr. Boucher also said Mr. al-Sadr's followers should hand over the police stations and other government offices they have seized to legitimate authorities.