Karzai said the campaign against the Taliban and al-Qaeda had faltered because of ongoing civilian casualties during Nato military operations and a lack of focus on "destroying the terrorists' refuge" across the border.
The Afghan government maintains that the US should be doing more on other fronts, including pressuring neighbouring Pakistan to shut down so-called insurgent sanctuaries.
Karzai's comments during a meeting with visiting US legislators come at a time when the US administration is ratcheting up pressure on the Afghan leader to do more to stamp out corruption.
Retired US Army General Jack Keane told Al Jazeera that the US decision to withdraw troops from Afghanistan was a mistake, and that Karzai's views were widely held in the region.
"Just the policy itself has done damage in the region because it has clearly has encouraged our adversaries and put scepticism in the minds of our friends," he said.
Keane said in reality the move has made it tougher for the US "even if that policy is [conditional] and even if there was very little withdrawal in July".
Bob Inglis, one of the four US congressmen who met Karzai, said the Afghan president focused mainly on private contractors and the role of Afghan forces in the war on terror.
Karzai has ordered all Afghan and international security contractors to cease operations by the end of the year, saying they have abused Afghan civil rights and undermined the authority of the state.
Inglis told the Associated Press that Karzai emphasised that Afghan forces should take the lead when entering villages to clear out the Taliban, accompanied by US soldiers playing a supporting role.
"I was glad he said that because it indicated a level of ownership and commitment to Afghans taking charge of the task," Inglis said.
|The US plans to withdraw troops from Afghanistan in July next year [AFP]
But added, "I think it's an open question as to whether the Afghan security forces [are] at that level as of yet".
Following the recent release of classified US military documents by Wikileaks, the whistleblower website, Afghan officials have become more outspoken in urging the US to put more pressure on Pakistan to shut down terror sanctuaries.
The Pakistanis point to military operations against the Pakistani Taliban but say their forces are overstretched, especially after the recent floods forced the military to take a major role in relief operations.
Rangin Dadfar Spanta, Karzai's national security adviser and former Afghan foreign minister, in a commentary published on Monday in The Washington Post said Pakistan "continues to provide sanctuary and support" to the Taliban, al-Qaeda and other terrorist networks.
"The international community is present in Afghanistan to dismantle these international terrorist networks," he wrote.
"Yet the focus on this fundamental task has progressively eroded and has been compounded by another strategic failure – the mistaken embrace of 'strategic partners' who have, in fact, been nurturing terrorism."