( AP )- President Bush's top diplomat in Iraq said Friday that the U.S. plans to keep combat troops there into 2009, seen as the tipping point for establishing the nation's long-term security, and he offered no deadline for a full withdrawal.
Ambassador Ryan Crocker told The Associated Press that he can't make any promises if, as the Democratic candidates have signaled, the next president pulls forces out faster or in greater numbers.
Crocker said America remains "a center of gravity" in Iraq almost five years after invasion, and that violence and political development both hinge to a considerable degree on whether U.S. forces remain there.
Crocker said he and Gen. David Petraeus , the top U.S. military commander in Iraq, would make the best of any change in plans ordered from the top.
"Obviously, we're not the ones who make the policy decisions - not in this administration and not in the next one," Crocker said. "If someone wants to reset the conditions, then obviously we'll do the best we can within the context but those aren't assumptions that we start with."
Sens . Hillary Rodham Clinton, D-N.Y., and Barack Obama , D-Ill., have said they would begin withdrawing forces quickly if elected - Obama would bring all combat forces home within 16 months. Clinton has not set a deadline but says she wants to bring most home inside one year.
Both candidates would phase out the withdrawals - and leave a small number of forces behind for specific missions. Either Clinton or Obama is expected to become the Democratic nominee.
Republican front-runners Sen. John McCain of Arizona and former Massachusetts Gov. Mitt Romney say they would essentially continue Bush's strategy of bringing troops home only as conditions warrant.
The Iraq chiefs are working off a blueprint that calls for "conditions-based withdrawal," Crocker said. That could bring combat troops home by sometime next year if security conditions allow it but leave other forces in Iraq for long-haul missions such as training.
Crocker said the two men stand by an earlier assessment that Iraq would be more or less secure and stable by summer of 2009. American combat troops will be needed at least into 2009 to battle a resilient al- Qaida and still-vibrant insurgency, he said.
Crocker and Petraeus will make their next report to Congress in April. Crocker would not speculate on whether Bush's planned force drawdown would continue after this summer, and he offered no firm predictions on how long any troops would remain.
Bush has indicated he is willing to leave more troops in Iraq at the close of his presidency than envisioned only weeks or months ago. The president said last month that it's fine with him if Petraeus wants to "slow her down" to meet current security needs.
One Army brigade and two Marine battalions have already returned home and will not be replaced. Four other Army brigades are to depart by July, leaving 15 brigades, or roughly 130,000 to 135,000 troops in Iraq. Those troops were part of Bush's 2007 escalation to confront a steep rise in violence, especially in Baghdad.
The escalation worked, within limits, to reduce violence in the capital and allow what Crocker called a returning sense of normalcy. He spoke, however, hours after coordinated suicide bombings that killed at least 73 people at outdoor markets in Baghdad. It was the single deadliest day in Iraq since Washington flooded the capital with 30,000 extra troops last spring.
Secretary of State Condoleezza Rice said the bombings prove al- Qaida is "the most brutal and bankrupt of movements" and will strengthen Iraqi resolve to reject terrorism. The bombs were strapped to two mentally disabled women and set off by remote control. The women may have been unknowing agents of death.
Crocker will be the top U.S. negotiator in talks on the American presence with the Iraqis expected to begin this month. He said he expected an eventual "status of forces agreement" to allow for great flexibility in pursuing insurgents while not setting definite troop levels.
"I don't think al- Qaida is going to have gone away after this year, and we and the Iraqis are going to want to make sure we are able to pursue them, but questions of force levels and what not, those will be executive decisions by this president and by the next," he said. "This agreement is in no way going to get into that executive decision prerogative."
Crocker also said that Iran continues to play a negative role in training and supplying insurgents with weapons and explosives, but the ambassador made clear he remains open to renewing a three-way security dialogue with Iranian and Iraqi officials.
A new meeting among the three sides could happen in "the next week or so," he said. But he noted that he had expected such talks to take place in early January after the United States indicated it was willing to participate a month earlier.
"The Iranians may be ready to come back to the table and if they are, we'll be there," Crocker said. "I am perfectly ready to sit down with my counterpart and would expect to do so."
However, he said a lower-level meeting of security officials probably would precede any ambassadorial meeting, which would be his fourth with the Iranian ambassador to Iraq since he arrived in Baghdad nearly one year ago.
Another Iraqi neighbor, Syria, which Washington accuses of allowing foreign fighters to enter Iraq from its territory, appears to have clamped down on such border crossings, Crocker said.
"We have seen a downturn in the number of suicide bombers coming across" the border and that "was not just a coincidence," he said.