ISLAMABAD, Pakistan - U.S. Secretary of State Hillary Rodham Clinton was confronted repeatedly by Pakistanis Friday as she ended a tense three-day tour of the country, chastised by one woman who said a U.S. program using aerial drones to target terrorists amounted to "executions without trial."

On another thorny topic, Clinton slightly softened her blunt charge of a day earlier that Pakistani officials know where al-Qaida terrorists are hiding and are doing little about it.

Clinton faced sharp questions from Pakistani civilians about the U.S. effort that uses unmanned aircraft to launch missiles to kill terrorists along the porous, ungoverned border with Afghanistan.

But she refused to go into detail about the classified strikes that have killed both key terror leaders and bystanders, long a source of outrage among Pakistan's population despite an equally deadly campaign of militant-spawned bombings.

Asked repeatedly about the drones, a subject that involves highly classified CIA operations, Clinton said only that "there is a war going on." She added that the Obama administration is committed to helping Pakistan defeat the insurgents.

Clinton left Islamabad for Abu Dhabi in the United Arab Emirates after a tour that was rocked at the start by a devastating terrorist bombing in Peshawar that killed 105 people, many of them women and children.

Her visit revealed clear signs of strain between the two nations despite months of public insistence that they were on the same wavelength in the war on terror.

What is less apparent is what U.S. officials hope will come from Clinton's tough language about Pakistani officials' failure to eliminate al-Qaida as a threat within their borders. While her remarks echo the skepticism that many Americans have felt about Pakistan's failure to target al-Qaida's leaders, it is not at all certain that they will prod stepped-up action.

Pakistan's military recently launched a major offensive in the South Waziristan border area to clear out insurgent hideouts. But two earlier army efforts made little progress there -- leaving questions about the military's resolve to tackle al-Qaida head-on.

Two U.S. defence officials said Friday that the latest Pakistani sweep into South Waziristan, though still early, was making progress. The officials spoke on condition of anonymity to talk about the Pakistani offensive.

Before she flew to the emirates Clinton carefully scaled back her comments from a day earlier suggesting that some Pakistani officials knew where al-Qaida's upper echelon has been hiding and have done little to target them.

When the U.S. gathers evidence that al-Qaida fugitives are hiding in Pakistan, Clinton said Friday during a Pakistani media interview, "We feel like we have to go to the government of Pakistan and say, somewhere these people have to be hidden out."

"We don't know where, and I have no information that they know where, but this is a big government. You know, it's a government on many levels. Somebody, somewhere in Pakistan must know where these people are. And we'd like to know because we view them as really at the core of the terrorist threat that threatens Pakistan, threatens Afghanistan, threatens us, threatens people all over the world," Clinton said.

During an interview Friday on ABC's "Good Morning America," Clinton was asked if she thought Pakistan was harbouring terrorists, saying: "I don't think they are. ... But I think it would be a missed opportunity and a lack of recognition of the full extent of the threat, if they did not realize that any safe haven anywhere for terrorists threatens them, threatens us and has to be addressed."

A day earlier she had been more explicit in her skepticism, telling a Pakistani journalist in Lahore: "I find it hard to believe that nobody in your government knows where they are and couldn't get them if they really wanted to. Maybe that's the case. Maybe they're not gettable. I don't know."

A top Pakistan official insisted Friday, in comments meant as a response to Clinton, that his country is fighting back against militants. "We have decided to fight back," Interior Minister Rehman Malik said, alongside Clinton at a police training centre.

Late Thursday, Pakistani army officers displayed two passports seized from a suspected terror hideout in South Waziristan and believed linked to terror operatives.

In Washington, White House spokesman Robert Gibbs said Clinton's tough remarks were "completely appropriate." Clinton echoed what U.S. officials tell the Pakistanis in private and do not undermine Pakistani co-operation, he said.

As for the drone aircraft armed with guided missiles, the program is credited by U.S. officials with eliminating a growing number of senior terrorist group leaders this year who had used the tribal lands of Pakistan as a haven beyond the reach of American ground forces in Afghanistan.

During an interview with Clinton broadcast live in Pakistan with several prominent female TV anchors, before a predominantly female audience of several hundred, one member of the audience said the Predator attacks amount to "executions without trial" for those killed.

Another asked Clinton how she would define terrorism.

"Is it the killing of people in drone attacks?" she asked. That woman then asked if Clinton considers drone attacks and bombings like the one that killed more than 100 civilians in the city of Peshawar to both be acts of terrorism.

"No, I do not," Clinton replied.

Another man told her bluntly: "Please forgive me, but I would like to say we've been fighting your war."

After arriving in Abu Dhabi, Clinton was expected to meet Saturday with Palestinian President Mahmoud Abbas.