The remarks from Sen. Carl Levin of Michigan, chairman of the Senate Armed Services Committee, are a preview of the possible roadblocks Obama faces from his own party as he begins to sell a broader, more expensive battle plan for Afghanistan to an American public weary of the conflict.

Greater numbers of Afghan army and police are central to succeeding in the 8-year-old war, according to Levin, and more U.S. trainers and an infusion of battlefield gear will help meet that goal. But it's unclear, Levin said, what role tens of thousands of additional U.S. combat troops will play in that buildup, and Obama has to make a compelling case during a national address he's scheduled to give Tuesday night from the U.S. Military Academy at West Point, N.Y.

"The key here is an Afghan surge, not an American surge," Levin said. "We cannot, by ourselves, win (the) war."

At West Point, Obama is expected to announce an increase of up to 35,000 more U.S. forces to defeat the Taliban-led insurgency and stabilize a weak Afghan government. The escalation, which would take place over the next year, would put more than 100,000 American troops in Afghanistan at an annual cost of about $75 billion.

Obama is also expected to outline an exit strategy for the war.

Democrats concerned over the price tag have proposed a war tax to pay for operations. Rep. David Obey, D-Wis., chairman of the House Appropriations Committee, has introduced legislation to impose a war surtax beginning in 2011. The bill would exempt service members and their families.

"If this war is important enough to engage in the long term, it's important enough to pay for," Obey said.

Lawmakers also want a greater commitment from NATO allies so the U.S. isn't footing the bill on its own.

"I've got a real problem about expanding this war where the rest of the world is sitting around and saying, 'Isn't it a nice thing that the taxpayers of the United States and the U.S. military are doing the work that the rest of the world should be doing?'" said Sen. Bernie Sanders, I-Vt.

British Prime Minister Gordon Brown has said that several allied nations will offer a total of 5,000 more troops. Speaking Saturday at a news conference in Trinidad, Brown also said Afghan President Hamid Karzai's government must meet specific benchmarks that allow foreign troops to gradually hand over control of the fighting to local forces.

Sen. Richard Lugar of Indiana, the top Republican on the Foreign Relations Committee, said he was wary of strict benchmarks that put both sides in an untenable situation if they're not met. But he said an early test of success will be whether Afghan forces can hold onto southern parts of the country after the U.S.-led coalition succeeds in chasing out the Taliban.

With Obama's Afghanistan speech coming as the Senate takes up the debate over the health care overhaul, Lugar recommended that Congress postpone the health care effort until next year so lawmakers can concentrate on how to finance the war.

"The war is terribly important," Lugar said. "I would suggest we put aside the health care debate until next year ... and talk now about the essentials: the war and money."

But Sen. Jack Reed, D-R.I., said health care legislation is at a critical stage and passing it is too important to the economy and American businesses. "We have to go ahead and conclude this debate," he said.

Reed, also a member of the Armed Services Committee, said he is looking for Obama to spell out a detailed strategy that reaches beyond Afghanistan and involves protecting the U.S. from al-Qaida. That involves being influential in neighboring Pakistan and a combination of intelligence, counterterrorism and counterinsurgency operations, he said.

Reed said the key element is shifting the operations to the Afghanis. "And if that can be done, then I would support the president," Reed said.

Army Gen. Stanley McChrystal, the top commander in Afghanistan, wants an overall Afghan security force of 400,000 — 240,000 soldiers and 160,000 police officers — by October 2013.

Levin has proposed moving that date forward a year to 2012. He says the manpower is available to support the faster timetable.

A new Senate Foreign Relations Committee report about the failure to kill or capture Osama bin Laden in Afghanistan's rugged Tora Bora region in December 2001 underscores the Bush administration's mistake of concentrating more on Iraq than Afghanistan, Levin added.

"We took our eye off the ball," Levin said. "Instead of moving in on him at Tora Bora, the previous administration decided to move its forces to Iraq. It was a mistake then. And I think this report ... just sort of reinforces that."

Levin appeared on CBS' "Face the Nation." Lugar, Reed and Obey appeared on CNN's "State of the Union." Sanders appeared on ABC's "This Week."

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