"I don't think that we'll be able to finalize this agreement by next Thursday," said spokeswoman Dana Perino, referring to the July 31 date that the administration had hoped to meet.

"We are working towards it but it might take a few more days after that," she said.

Perino said earlier that the planned US-Iraq long-term strategic agreement will not include a specific date for a withdrawal of US combat troops.

"What it will not do is have any sort date tied to combat troops, like how many American troops would be in Iraq at X date. That would not be included," she told reporters.

But the pact is expected to include an "aspirational date" for Iraqis to take over security for all of the war-torn country's provinces, she said amid a confused back and forth between Baghdad and Washington on the issue.

"It might be something along the lines of 'we think that Iraq would be able to take over its security for all of its provinces by this aspirational date,'" Perino said.

"But I don't know exactly how it's going to read, but it would not include anything about troop levels," she said amid a bitter back and forth on the issue between the leading US presidential hopefuls ahead of November elections.

"This commander in chief is not going to tie the hands of the next commander in chief, whoever it is," the spokeswoman said.

Asked whether US forces would have to leave if Iraq's government asked them to, Perino said US President George W. Bush has already said "we would do that" but underlined "nobody is talking about that."

"We share the goal of trying to bring more of our combat troops home and transitioning our mission into one where they could help the Iraqis and back them up," said Perino. "We are there because the Iraqis want us there."

"We don't want to do it in a way that unravels the gains."

© 2008 Agence France-Presse