WASHINGTON -- Confronting the prospect of failure after seven years in Afghanistan, the U.S. military is crafting a new strategy that probably will expand the power and reach of tribal militias while relying less on the increasingly troubled central government.

Under the new approach, U.S. forces would scale back combat operations to focus more on training both of government forces and tribal militias. The plan is controversial because it could extend the influence of warlords while undermining the government of President Hamid Karzai in Kabul.

At the same time, the new strategy could set up a hair-trigger rivalry between national security units and the improved tribal forces, proponents concede.

The U.S. military's willingness to consider such risks reflects the growing worry about worsening conditions in Afghanistan. Until recently, the military would not have considered a move to bolster tribal militias, but -- with relatively few troops available -- military leaders believe that only a new approach to the war can stanch the spreading violence.

"There has been very, very tough fighting this year, and it will be tougher next year unless we adjust," Adm. Michael G. Mullen, chairman of the Joint Chiefs of Staff, told reporters yesterday.

Supporters contend that the dangers are offset by the prospect that well-trained tribal forces could help improve local security, undercut the insurgency and strengthen ties between rural areas and the central government. "My bottom line is that this is clearly something we should do," said a senior military officer, who was one of several to describe strategy reviews on condition of anonymity because they are still under way.

By focusing on tribal militias and local security, the new approach resembles the U.S. campaign in Iraq, where former Sunni insurgents were paid to shift their allegiance. But American officers stress that they are not planning to export the troop surge used in Iraq -- a topic of debate and commentary during the intensifying U.S. presidential campaign -- to Afghanistan, where there are fewer U.S. troops and differing fault lines among ethnic groups.

The new approach also reflects increasing frustration among U.S. and allied commanders over Afghanistan's central government, which they believe has been proved too weak to exert any meaningful influence outside the capital, especially in the country's mountainous reaches.

Although Mr. Karzai several years ago declared that the era of warlordism was over and offered several warlords influential posts in the central government, warlords remain extremely powerful forces in the Afghanistan. Many enjoy great influence in their home provinces, with some fielding private militias or gaining wealth from the opium trade.

Any broad effort to train tribal militias probably would have U.S. military forces working with Taliban sympathizers. But U.S. Defense Secretary Robert M. Gates, who is in Budapest, Hungary, to discuss the Afghanistan war with NATO defense ministers, yesterday said the United States would be open to reconciling with the Taliban.

"There has to be ultimately -- and I'll underscore ultimately -- reconciliation as part of a political outcome to this," Mr. Gates said. "That's ultimately the exit strategy for all of us."

The new Afghan strategy is being crafted as new intelligence assessments conclude that Afghanistan is spiraling downward, in part because of the government's shortcomings and widespread corruption. Those findings, contained in an upcoming U.S. National Intelligence Assessment, pose new concerns for U.S. forces in Afghanistan, which have reported successive years of record casualties in 2007 and 2008.

The strategy shift is emerging from reviews set in motion earlier this year and nearing completion. The Pentagon and White House both are conducting such reviews, and the U.S. Central Command, the military headquarters in charge of U.S. forces in the Middle East, is crafting its own recommendations.

Results of the White House review, under Lt. Gen. Douglas Lute, deputy national security adviser for Iraq and Afghanistan, are weeks away, according to an administration official.

The military reviews, one ordered by Adm. Mullen and the other by Gen. David H. Petraeus, incoming head of the Central Command, might be more significant because they could guide options presented to the next administration.

There are more than 30,000 U.S. troops in Afghanistan, far fewer than the 140,000 in Iraq. Military officials hope to send as many as 15,000 new troops in 2009, but some members of the Joint Chiefs have insisted that no additional forces should be sent until a new strategy is in place.

An acute need is for military trainers, both for regular Afghan forces and for the militias, as part of the U.S. push to improve local security.

The new Pentagon plan would expand the military trainers in Afghanistan by giving combat troops added responsibilities. Currently, most units are assigned either to a combat or training role.