WASHINGTON/KABUL - The top U.S. and NATO commander in Afghanistan says in a confidential assessment of the war that without additional forces the mission will likely result in failure.

A request for more troops faces resistance from within U.S. President Barack Obama's Democratic Party, which controls Congress, and opinion polls show Americans are turning against the nearly eight-year-old war.

Army General Stanley McChrystal wrote: Failure to gain the initiative and reverse insurgent momentum in the near-term (next 12 months) -- while Afghan security capacity matures -- risks an outcome where defeating the insurgency is no longer possible.

The assessment is contained in a copy of the 66-page document obtained by The Washington Post. McChrystal's spokesman in Kabul confirmed that the document is genuine.

McChrystal is expected to ask for a troop increase in the coming weeks to stem gains by a resurgent Taliban.

The Post said the McChrystal assessment makes clear that his call for more forces would be part of a new strategy that emphasizes protecting Afghans rather than killing insurgents.

Inadequate resources will likely result in failure. However, without a new strategy, the mission should not be resourced, McChrystal is quoted as saying.

McChrystal has finished preparing his request, which some officials expected would include roughly 30,000 new combat troops and trainers, but he has yet to submit it to Washington for consideration.

Defense Secretary Robert Gates has said the Pentagon was working with McChrystal on how that request should be made.

In the assessment, McChrystal paints a grim picture of how the war is progressing and writes the overall situation is deteriorating.

He calls for a dramatically and even uncomfortably different approach to fighting a war which requires a cultural change in the way the military fights.

The objective is the will of the people, our conventional warfare culture is part of the problem, the Afghans must ultimately defeat the insurgency.

The war in Afghanistan is now at its deadliest in eight years. McChrystal's assessment says fighters have control over entire sections of the country, although it is difficult to say how much because of the limited presence of NATO troops.

He also strongly criticizes the Afghan government as having lost the faith of the country's people.

The weakness of state institutions, malign actions of power-brokers, widespread corruption and abuse of power by various officials, and ISAF's own errors, have given Afghans little reason to support their government, McChrystal says, refering to the International Security Assistance Force.

WASHINGTON RESISTANCE

The number of U.S. troops in Afghanistan has almost doubled this year from 32,000 to 62,000 and is expected to grow by another 6,000 by the year's end. There are also some 40,000 troops from other nations, mainly NATO allies.
Fifty-eight percent of Americans now oppose the Afghan war while 39 percent support it, according to a recent CNN/Opinion Research poll.

Obama said in interviews aired on Sunday he wants to wait to determine the proper strategy for U.S. forces in Afghanistan before considering whether more troops should be sent there.

I just want to make sure that everybody understands that you don't make decisions about resources before you have the strategy ready, he told ABC.

Congressional critics, including his 2008 Republican presidential opponent Senator John McCain, have urged the administration to approve the deployment of more troops immediately, saying any delay puts the lives of troops already in Afghanistan at greater risk.

Senate Republican leader Mitch McConnell told CNN on Sunday his party would be supportive of a U.S. troop increase for Afghanistan if it was needed as part of a new strategy but he said he was troubled by the delay in the decision-making.

We think the time for decision is now, McConnell said.

(Writing by JoAnne Allen; Editing by Nick Macfie)