US lawmakers celebrating Osama Bin Laden's death are worried that his slaying would mute a rallying cry for the war effort in Afghanistan and expressed fresh doubts about success there.
US forces poured into the country after the September 11, 2001 attacks, ousting the Taliban militia from power after they refused to hand over the Al-Qaeda chief who masterminded the worst strikes on US soil.
"With the death of Bin Laden, some people are sure to ask, 'Why don't we just pack up and leave Afghanistan?'" Senate Foreign Relations Committee Chairman John Kerry said as his panel examined US goals in the nearly 10-year conflict.
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Kerry noted that President Barack Obama faced a key decision with the planned July start date for a US troop draw-down designed to end with the handover of security responsibilities to Afghan forces in 2014.
But with cash-strapped Washington a $120-billion price tag this year alone for the war effort, "we have to ask at every turn if our strategy in Afghanistan is sustainable," said the Democratic senator.
Kerry said he would travel to Afghanistan at the end of next week to see whether the Al-Qaeda mastermind's end had improved the odds of getting Islamist Taliban fighters to lay down their arms, securing more help from Pakistan, and pushing the fragile government in Kabul to do more to help
But Senator Dick Lugar, the top Republican on the committee and Obama's foreign policy mentor when he was in the senate, warned it was "exceedingly difficult" to justify sustained US commitments in Afghanistan as "rational."
"With Al-Qaeda largely displaced from the country but franchised in other locations, Afghanistan does not carry a strategic value that justifies 100,000 American troops and a $100 billion per year cost, especially given current fiscal restraints in the United States," said Lugar.
US lawmakers who must approve annual and emergency military outlays face a political climate in which angry voters demand deep cuts to virtually every area of government, including in foreign aid and at the Pentagon.
And with some 1,600 US troops dead since 2001, even those in Washington who supported the invasion worry that uncertain odds of success no longer justify the US presence in the strife-torn country.
Number-two Democratic Senator Dick Durbin worried that he had voted "for the longest war in American history, which has no end in sight, even after the killing of Osama Bin Laden."
The White House -- which needs Republican support to keep Obama's strategy funded -- said Tuesday it would stick to its plan.
"The operation continues. The July 2011 transition date for the beginning of a drawdown remains very much in place. The pace of that drawdown will be determined by conditions on the ground," said spokesman Jay Carney.
And Democratic House Minority Leader Nancy Pelosi urged patience on those who would see Bin Laden's death as a sign US forces must come home now.
"We are on a track to come home from Afghanistan, beginning in July 2011 we begin that path," she told reporters.
"Change is in the air there, and now it is even more so in light of" the terrorist mastermind's slaying.
Speaking to Kerry's committee, Richard Haass, who helped shape US policy towards Afghanistan under former president George W. Bush, called the war effort "a strategic distraction, pure and simple."
Haass said current policy was on course for failure but advocated a sharp draw-down to 10,000 to 25,000 troops who could carry out counter-terrorism operations and warned "walking away...is not the answer."
That led Durbin to shake his head and ask Haass: "How can we send one more American soldier to fight and die in Afghanistan?"
The question seemed an eerie echo of Kerry's testimony before the committee in 1971 as it explored US options in the Vietnam War, when he asked "How do you ask a man to be the last man to die for a mistake?"
Democratic Senator Bob Casey later told AFP that US policy in Afghanistan "is not debated enough here in Washington, it's not part of our discussions enough around dinner tables.
"We've got a decision to make," he said.
