Iraqi President Jalal Talabani said that American troops can set up bases in northern Iraq's Kurdish region only if the Shiite-led government in Baghdad gives its approval.
"It is not possible for U.S. troops to stay in Kurdistan without the approval of the central government," Talabani said in an interview with state television Al-Iraqiya late on Sunday.
"Kurdistan is part of Iraq, and all of the country's constitutional laws apply to it."
His remarks came after Massud Barzani, the president of the northern Kurdish administration of Iraq, said on a visit to Washington that the U.S. military could have bases in the north if Washington and Baghdad failed to sign a controversial security deal.
The deal will decide the future presence of U.S. troops in Iraq beyond 2008.
Local Iraqi newspaper "Khabat" quoted Barzani as saying that his regional government would "welcome" such a move.
"All the attempts are going right now to sign the pact, but if the pact is not signed and if U.S. asked to keep their troops in Kurdistan, I think the parliament, the people and government of Kurdistan will welcome this warmly," he said at the Centre for Strategic and International Studies in Washington.
Barzani has strongly backed the controversial security deal, but its signing was delayed after the Iraqi cabinet decided to seek changes in the latest draft of the agreement.
Barzani and other Iraqi Kurdish leaders have been strong U.S. allies since the 1991 Gulf War that pushed former dictator Saddam Hussein's troops out of Kuwait and established a no-fly zone over the country's northern Kurdish region.
Anti-American Shiite cleric Moqtada al-Sadr's group also criticized Barzani over his comments.
"We reject the statement by Massud Barzani," sheikh Saleh al-Obeidi, spokesman for the group, told AFP.
"This position reminds us that Kurds want to separate. There is a constitution in this country and they have to respect it."