Senior US officials have begun debating whether George Bush, the US president, should announce his intention to withdraw US troops from Iraq.

The New York Times reported that Bush had originally been mulling over a September 15 deadline to announce a pullout, when a progress report on Iraq is due to be released.

But the US president's aides have advised him that he may need to make an announcement sooner ahead of a senate debate on the defence authorisation bill, the report said.

Many Republican senators have recently announced they can no longer support Bush's Iraq strategy and have demanded change.

As a result, the paper reported some aides are now telling Bush that if he wants to forestall more defections, it would be wiser to announce plans for a far more narrowly defined mission for US troops that would allow for a staged pullback.

The president had originally rejected this strategy in December when it was proposed by the bipartisan Iraq Study Group.

"When you count up the votes that we've lost and the votes we're likely to lose over the next few weeks, it looks pretty grim," the New York Times quotes one senior official as saying.

In a sign of growing concern in the administration, Robert Gates, the US defence secretary, cancelled his Latin American tour on Sunday to attend meetings on Iraq.

Last week, Stephen Hadley, US national security advisor, was called in from a brief holiday to join discussions on Iraq, which included Karl Rove, a US political strategist and Joshua Bolten, the White House chief of staff, according to the report.

Deep concern

Officials describe Hadley as deeply concerned that the loss of Republicans could accelerate this week, a fear shared by Rove, the report said.

But they also said that Rove had warned that if Bush went too far in announcing a redeployment, the result could include a further cascade of defections - and the passage of legislation that would force a withdrawal by a specific date, the paper said.

"Everyone's particularly worried about what happens when McCain [John, a Republican senator] gets back from Iraq," one official is quoted as saying.

McCain has been a strong supporter of the "surge" strategy, but is facing political troubles in the race for the Republican nomination for president.

McCain's poor performance in presidential nomination polls, attributed to his position on Iraq, has fuelled speculation that he may declare that the Iraqi government is incapable of reaching the kind of political accommodations that Washington considers necessary for overall success, the New York Times said.