US Secretary of State Condoleezza Rice has defended tactics used in the fight against al-Qaeda militants amid growing anger towards the US in Pakistan.
Thousands of Pakistanis have been protesting against the US
Protesters in Pakistan have blamed the US for the deaths of 18 civilians in a missile attack on a village on Friday.
Ms Rice did not say if the US carried out the attack, the intended target of which, according to media reports, was al-Qaeda number two Ayman al-Zawahiri.
Islamabad has protested to the US, saying the strike missed its target.
Jets, or in some accounts an unmanned aircraft, reportedly fired missiles at a housing compound in the village of Damadola, near the Afghan border, on Friday.
Pakistan's Islamic opposition parties have led street protests against the attack, accusing the US of killing innocent civilians and violating Pakistani sovereignty.
"America raised the bogey of Zawahri to provide justification for this attack," Meraj ul-Huda, an opposition leader, told a rally in the city of Karachi.
Ms Rice said tough tactics are necessary in the fight against al-Qaeda.
"We'll continue to work with the Pakistanis and we'll try to address their concerns," she said on Monday.
Describing the country as an ally in the "war on terror", she said al-Qaeda and its supporters "are not people who can be dealt with lightly".
She said she could not comment on any specific circumstances.
Thousands of Pakistanis have been taking to the streets across the country to protest at the attack.
Hundreds of people have also been travelling to see the remains of the houses flattened by the strike in Damadola.
Among them was a local Islamic militant commander and fugitive, Maulana Faqir Mohammad, Pakistani daily The News reported.
He told the newspaper the US was linking Zawahiri to the village in order to cover up a botched strike.
Praising Zawahiri as a soldier of Islam, Mr Mohammed reportedly said: "I am a small man with few resources but I would offer him refuge if he made a request".
Pakistani Prime Minister Shaukat Aziz is the latest high profile figure to condemn the attack, the Associated Press news agency reported.
Speaking on the eve of a visit to the US, where he plans to discuss the economy and security issues, Mr Aziz said Friday's incident, though "regrettable", did not take away "from the fact that Pakistan needs investment".
Osama Bin Laden's top aide, Mr Zawahiri has eluded capture since the US overthrew the Taleban in Afghanistan in 2001.
The US has about 20,000 troops in Afghanistan, but Pakistan does not allow them to operate across the border.