President Barack Obama held a final strategy session with top aides on whether to send more US troops to Afghanistan and plans to announce his decision within days, the White House said.

The session in the Situation Room yesterday with officials including Vice President Joe Biden, Secretary of State Hillary Clinton and Defence Secretary Robert Gates marked the ninth such meeting.

Obama is nearing a decision on whether to add as many as 40,000 troops to an eight-year-old war that began after the September 11 attacks and has begun to try the patience of US citizens.

"After completing a rigorous final meeting, President Obama has the information he wants and needs to make his decision and he will announce that decision within days," White House spokesman Robert Gibbs said in an email.

Obama's announcement is widely expected to come before a NATO meeting on December 7 in Europe in which alliance members could agree to send thousands of additional trainers.

There are about 110,000 foreign troops, including 68,000 US soldiers, in Afghanistan fighting Taliban insurgents.

Obama has been reviewing war strategy in Afghanistan for the past two months after Army General Stanley McChrystal, the top US commander there, said in a report that conditions were deteriorating and 40,000 additional troops were needed as the minimum to quell the insurgency.

Obama's top national security advisers, including Gates and Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, are believed to have rallied around options that would send 30,000 to 40,000 more troops and trainers.

Obama faces conflicting pressures on Afghanistan.

Americans are divided about whether to send more troops. Republicans in Congress insist more troops are needed to prevent a Taliban resurgence, while his fellow Democrats in general would like to see the United States find a way out of Afghanistan.

Two veteran Democratic lawmakers have called for imposing a "war tax" to pay for a troop increase. The two are David Obey, chairman of the House of Representatives Appropriations Committee, and Carl Levin, chairman of the Senate Armed Services Committee.

A congressional aide said that under the idea, families earning less than US$150,000 a year would be taxed at 1 percent of their tax rates. The tax would be higher for those in the US$150,000-to-US$250,000 range and those making $250,000 or more.

Democratic Senator Daniel Inouye, chairman of the Senate Appropriations Committee, opposed it. "Someone has to demonstrate how it can be done," he said.

Gibbs said it was premature for him to comment since Obama had yet to settle on a troop plan.