"Wake Up America. WikiLeaks' release of secret war documents gave us 92,000 reasons to end the wars. Pick one," Democratic Representative Dennis Kucinich, author of the Pakistan measure, said as debate began.
Debate on funding
House Democratic Majority Leader Steny Hoyer left open the possibility of "further debate" on the strategy and the presence of US troops, but stressed "until we bring them home they need that money."
And Representative Buck McKeon, top Republican on the House Armed Services Committee, invoked US forces on the frontlines and declared that "cutting off their funding in the middle of that fight is tantamount to abandonment."
But Democratic Representative Dave Obey, chairman of the powerful appropriations committee, said he would "reluctantly vote no" out of doubts "that this operation will hurt our enemies more than us."
US officials were grappling with the possible impact of the WikiLeaks disclosures, which appeared short on any blockbuster revelations but put fresh media focus on the unpopular conflict.
Pentagon spokesman Colonel Dave Lapan said an Army Criminal Investigation Division would be taking a "broad look" at the leaks of the military reports from 2004 to 2009 that paint an unsettling picture of a troubled war effort.
Foes of the war, now in its ninth year, were drawing strength from the leaks by the whistleblower's website, which seemed to buttress criticisms of the governments in Kabul and Islamabad.
Kucinich, who has previously called for an end to the Afghan war, said US money went to "a corrupt government in Afghanistan," or to "a corrupt government in Pakistan which helps the Taliban in Afghanistan kill our troops."
Democratic leaders hoped to have the "magic number" of votes to approve the war funding and predicted defeat of the so-called War Powers Resolution on Pakistan, named after a Vietnam-era law aimed at boosting congressional authority over US war-fighting, a leadership aide said.
'Pakistan helped insurgents'
The leaked files suggest that Pakistan's intelligence agency has been holding strategy sessionswith Taliban leaders to aid their efforts in Afghanistan.
Iranian President Mahmoud Ahmadinejad, meanwhile, denied in an interview with the US television network CBS that his government provided support to Taliban insurgents in Afghanistan.
"We do not support any group," Ahmadinejad said.
"We just and only support the Afghan people. We support and we want to strengthen security in Afghanistan."
The Obama administration and its allies in the US Congress, many of whom have expressed grave doubts about the conflict, sought to play down the impact of the leak and denied any shift in policy on Pakistan.
'Raw reports unreliable'
Senate Foreign Relations Committee chairman John Kerry said it was important not to "overhype" raw intelligence field reports, some of them "completely dismissible," others "unreliable."
"People need to be very careful in evaluating what they read there," the Democrat said, insisting Washington had "made some progress" in addressing the issue of Pakistan.
But Admiral Mike Mullen, the US military's top officer, denied the leaks raised questions over US relations with Pakistan, where US forces are hunting for top Al-Qaeda leaders along its shared border with Afghanistan.
Mullen told reporters that US-Pakistan ties had "dramatically" improved in the past year, but warned "any links which exist with terrorist organizations" and Pakistan intelligence services are "just completely unacceptable."
The former top US diplomat in Kabul, Ryan Crocker, worried about the public will to see the bitter conflict through "Impatience is on the rise again in this country," he told Kerry's committee, warning that a failure of US resolve was "what our adversaries are counting on now."