In a rare move, National Security Adviser Tom Donilon on Wednesday publicly defended the United States' use of armed drones in the counter-terrorism fight, calling it a "targeted effort."
Donilon addressed their controversial deployment after a student asked him about their use while he was speaking at Harvard University's Kennedy School of Government.
He said they are only used against groups and individuals who pose the most serious threats against the United States.
"We are using all of the tools," available to fight al Qaeda and one of those is the drones, Donilon said.
Donilon did not use the word drones in his answer. He called them UAVs-- unarmed aerial vehicles -- and said the U.S. is in "full compliance" with domestic and international law.
"We have the right to take action," he said, adding it is "done prudently."
Drones have become a key part of the counter-terrorism arsenal operating over Pakistan, Yemen, Afghanistan and Somalia.
The U.S. official said the possibility of collateral damage is taken into account, but called them a "wise tool" because a broader military attack would result in higher casualties.
He said the Obama administration has tried when it can to discuss in public the principles behind the use of drones -- their legal justification, when an American can be targeted -- but the sensitive nature of the missions limits what officials can say.
The Pakistani student who asked Donilon about drones also addressed the U.S. relationship with his home country.
Donilon admitted "it has had its challenges" and "we have had disagreements," but called Pakistan a "critical partner" in the counter-terrorism effort, pointing out it has lost thousands of its own forces.
He said the aftermath of the U.S. mission that killed Osama bin Laden was a "difficult moment" in the alliance. Pakistani officials were especially upset they were kept in the dark.
Donilon said U.S. officials knew their Pakistani counterparts would not be happy.
"We took that into account," he said, telling the audience that the U.S. knew there would be sovereignty questions, but the sensitivity of the mission required secrecy.
"We had to make that kind of judgment," he said.
He said the relationship today is better because there is no crisis.
On another key foreign policy issue facing the second term, the national security adviser also defended the administration's approach on Iran, saying the effort to prevent it from developing nuclear weapons was and remains a "top priority" in the president's second term.
Donilon said "tremendous pressure" has been applied on Iran's economy and that inflation and unemployment are being felt because of the sanctions put on the country.
He admitted one problem the west faces is making sure its message gets to the right people in the Iranian leadership "to try to force the point" that Iran must sit down and discuss its program. He said discussion is the only way to solve the problem.
"We will continue (the) pressure campaign," including politically isolating the country, Donilon said.