Nato's chief assured President Barack Obama yesterday of the alliance's commitment to the Afghan war as the US administration weighed sending more troops to try to turn the tide against a resurgent Taliban.

Promising that Nato will stay in Afghanistan "as long as it takes to finish our job", Nato Secretary-General Anders Fogh Rasmussen sought to ease Americans' doubts about whether their allies have the stomach to stay in the fight.

Public opinion in both the United States and Europe has turned increasingly against what Mr Obama's aides once hailed as the "good war", compared to the highly unpopular war in Iraq that occupied the focus of his predecessor, George W. Bush.

"Our operation in Afghanistan is not America's responsibility or burden alone: It is and it will remain a team effort," Mr Rasmussen said after White House talks with President Obama.

Mr Obama stressed the same point, insisting, "This is not an American battle, this is a Nato mission, as well," and he thanked Mr Rasmussen for committing the alliance to a "full partnership" in Afghanistan.

Mr Obama, who will meet top advisers about Afghanistan today, has said he will not decide on sending further US troops for Afghanistan until after a broad review of his administration's approach is finished. Mr Rasmussen said he agreed with Mr Obama's approach of "strategy first, then resources".

But in a sign of misgivings among US allies, Mr Rasmussen said in a speech on Monday European countries were likely to be more comfortable contributing trainers than combat troops. He stressed, however, that they had added 9,000 troops in the last 18 months.

The top US and Nato commander in Afghanistan, General Stanley McChrystal, has warned the Afghan effort would likely result in failure without a "significant change in strategy", which would also involve bringing in more troops.

He is believed to be seeking 30,000 to 40,000 combat troops and trainers, according to defence and congressional officials.

The Obama administration has already almost doubled its number of troops in Afghanistan this year to 62,000 to contend with the worst violence since US-led forces ousted the Taliban rulers in 2001.

Mr Obama now faces a fierce debate on the issue within his own administration as well as opposition from some of his fellow Democrats to an escalation of US forces. A decision is expected to take at least several weeks.