"We think the conference is certainly a step in the right direction in that it's important to see the government of Afghanistan addressing corruption issues," John Groch, a US embassy spokesman, said.
"At the same time, however, we're eager to see the government move forward with action."
Karzai has come under growing international pressure to take a tough line against government officials suspected of corruption, particularly in the wake of the fraud-tainted presidential poll that took place in August.
Karzai was declared the winner by default when Abdullah Abdullah, his main challenger, pulled out, citing irregularities.
Kai Eide, the senior United Nations representative in Afghanistan, had said earlier in October that there had been "widespread fraud" during the elections.
The calls for the Afghan government to crack down on corruption comes as thousands more US troops prepare to deploy to the country to battle fighters loyal to the Taliban and al-Qaeda.
Barack Obama, the US president, last week ordered 30,000 more soldiers to be sent to the country, following a request by the senior commander of US and Nato forces for more boots on the ground.
The US's senior military officer said on Monday he was increasingly concerned about the threat posed by Taliban and al-Qaeda fighters sheltering on the Pakistani side of the Afghan border.
Admiral Mike Mullen, chairman of the US joint chiefs of staff, said during a visit to Afghanistan that violence across the country was likely to become more severe in the coming months, with fighters holding the upper hand across about a third of Afghan provinces.
"I remain deeply concerned by the growing level of collusion between the Afghan Taliban and al-Qaeda and other extremist groups taking refuge across the border in Pakistan," Mullen said.
"Getting at this network, which is now more entrenched, will be a far more difficult task than it was just one year ago.
"The insurgency has grown more violent, more pervasive, more sophisticated," he said.
Mullen's comments came as a senior US commander in Afghanistan warned that the extra troop deployment would likely take longer than expected.
Lieutenant General David Rodriguez said that logistical challenges meant it would probably take nine to 11 months to deploy all the new troops to the region.
Obama's original plan had envisaged the additional deployment being in place within six months.
The initial vanguard of the 30,000 extra US troops – a 1,500-strong force of Marines - is expected to deploy to Afghanistan's southern province of Helmand later this week.
Washington has been trying to press the Pakistani government to push harder against Taliban and al-Qaeda fighters, who have long used the country as a refuge.