"It's not going to happen this week," Robert Gibbs, the White House spokesman, said. "Obviously the first possible time would be some time next week."

US officials and Western diplomats say they expect his announcement before a Nato meeting on December 7 in Europe in which alliance members could agree to send thousands of additional trainers to Afghanistan.

The US currently has nearly 68,000 troops deployed to fight a resurgent Taliban and al-Qaeda in Afghanistan.

Options

As Obama debates a revised strategy in the eight-year war, officials say he is considering four options.

Afghanistan options

The US currently has nearly 68,000 troops deployed to fight a resurgent Taliban and al-Qaeda in Afghanistan. As Obama debates a revised strategy in the eight-year war, officials say he is considering four options.

One option is the request put forward by the top US commander in Afghanistan, General Stanley McChrystal, for 40,000 more troops to secure the towns and cities.

Another option, said to be carrying the most favour among officials, is an increase of 30,000. Washington could then try to convince Nato allies to contribute, bringing the number of troops to the 40,000 McChrystal recommended.

Options three and four include significantly lower troop deployments, from 20,000 to 15,000, most of who would serve as trainers for the Afghan security forces.

One option is the request put forward by the top US and Nato commander in Afghanistan, General Stanley McChrystal, for 40,000 more troops to secure the towns and cities.

Another option, said to be carrying the most favour among officials, is an increase of 30,000. Washington could then try to convince Nato allies to make up the shortfall of 10,000.

Options three and four include significantly lower troop deployments, from 15,000 to 20,000, most of whom would serve as trainers for the Afghan security forces.
 
Obama and his advisers have debated options ranging from sending the tens of thousands more troops requested by McChrystal to limiting troop increases and concentrating on attacking al-Qaeda targets.

But reports have suggested that the advisers are rallying around options that would see a deployment of between 30,000 and 40,000 troops and trainers sent to Afghanistan.

Moves to send more troops face opposition from a public disillusioned with the long-running conflict and politicians from Obama's own Democratic party, who say the US must start looking for a way out of Afghanistan.

A Washington Post-ABC News poll found last week that 46 per cent of Americans support a large influx of troops to battle Taliban fighters and train the Afghan military, while 45 per cent favour a smaller number to focus on training Afghan security forces.

Obama's decision has also been complicated by concerns about corruption and governance in the administration of Hamid Karzai, the Afghan president.

Karzai was sworn in for a second term last week after an election marred by widespread fraud and farce as his main challenger refused to take part in a second round run-off.

Delays and doubts

Opposition Republicans, who tend to favour sending a large number of troops, have criticised Obama for taking as long as he has to decide.
 
Dick Cheney, the former vice-president, told a radio show on Monday that "the delay is not cost-free".

"Every day that goes by raises doubts in the minds of our friends in the region about what you're going to do, raises doubts in the minds of the troops."

Richard Holbrooke, Obama's special envoy for Afghanistan and Pakistan, hit back at critics who say Obama is dithering.

"I've seen a lot of these things. This is the most thorough, the most sustained, the most thoughtful process I have ever seen," he said , on Monday before the White House meeting.

"Over the long course of it, we have all learnt a great deal from each other in a way which I think is exactly the way a decision should be made."

Gibbs pointed out that the president was making "a complicated decision" and said: "I think the American people want the president to take the time to get this decision right, rather than to make a hasty decision," he said.

Meanwhile, the violence continues unabated, with seven soldiers, - four Americans and three Afghans - as well as five Afghan civilians killed in a series of attacks across the country in the past two days.