"There will not be bilateral talks between the United States and Iran, or the United States and Syria, within the context of these meetings," White House spokesman Tony Snow told reporters.
"These are organized by the Iraqis and these are on issues that are pertinent to Iraq," Snow said.
"As for whether the United States has changed its policy dramatically, it has not," he added, replying to speculation that joining the conference together with Tehran and Damascus was a sign of Washington’s warming toward the two US arch-rivals in the Middle East.
"We are not engaging in diplomatic recognition of Iran. We are not engaging in bilateral talks with Iran," Snow continued.
"A number of people have been characterizing US participation in a regional meeting as a change in policy, it is nothing of the sort," he emphasized.
Snow stressed that Iran, which he said was seeking diplomatic recognition from the United States, needed to change its policies before Washington engaged directly with them.
"They need to deliver," Snow said.
But, he added, "There are multilateral forums where, if the Iranians are there, we’re not going to walk out."
Snow spoke a day after Secretary of State Condoleezza Rice said the United States would attend a landmark conference on Iraq, which Iraqi Prime Minister Nuri al-Maliki fixed on Wednesday for March 10.
Maliki’s office said representatives of neighboring countries, permanent members of the UN Security Council, the United Nations, the Arab League and the Organization of the Islamic Conference were invited.
Snow did say that issues standing between the United States and Iran, including US accusations that Iranian operatives were contributing to the sectarian violence and attacks on US forces in Iraq, would not be avoided in the conference.
"If, in fact, topics like EFPs and such come up in that conference, obviously we will address them," he said, referring to the deadly "explosive formed penetrator" projectiles used against US forces that Washington says are being supplied to Iraqi insurgents from Iran.
Snow said the United States has previously joined regional meetings attended by Iran and Syria without changing its bilateral position toward either.
"The United States in a number of forums in the recent years has been at the table along with Iran and Syria on issues of regional concern … so this is not a crack in the wall, it is another example though of the United States working diplomatically," Snow said.
Bush previously has set out a tough stance on any diplomatic engagement with Iran and Syria.
Snow reiterated the US administration’s position on opening any dialogue with Iran, saying Tehran must first comply with UN Security Council demands to suspend uranium enrichment work "if they want to see us return to the table with them."