Obama defends US drone program, renews push to close Guantanamo

President Obama spoke in unprecedented detail Thursday about the U.S. drone program, as he adamantly defended the controversial strikes as legal and necessary to national security -- while announcing that he was setting new limits on their use.

The president for the first time personally acknowledged that U.S. drone strikes have killed several Americans overseas, only one of whom was targeted, after Attorney General Eric Holder made the information public a day earlier.

In a wide-ranging speech on counterterrorism policy, the president also renewed his call for the closure of Guantanamo Bay. Angering some Republican lawmakers, Obama urged Congress to lift restrictions on transferring detainees and revealed the Defense Department is now looking for a U.S.-based site to hold military commissions.

But much of the address was devoted to addressing long-standing concerns about the drone program. He confirmed that, a day earlier, he signed a directive setting guidelines for the strikes -- he said the strikes will only be authorized against terrorists who pose a "continuing and imminent threat" to Americans, and when there is a "near-certainty" that civilians will not be killed or hurt. He also said he's open to new proposals for congressional oversight.

Obama argued that the program operates under heavy constraints. He claimed the alternative, in some cases, is too risky or difficult -- as some areas where terrorists have taken refuge are remote and beyond the reach of the local government.

"It is in this context that the United States has taken lethal, targeted action against Al Qaeda and its associated forces, including with remotely piloted aircraft commonly referred to as drones," he said.

Obama said the strikes are legal, as America is at war.

"Simply put, these strikes have saved lives," Obama said.

The president addressed the program in a speech on counterterrorism policy at the National Defense University in Washington, D.C.

He also spoke in detail about his long-stalled effort to close Guantanamo Bay. He said that the administration is looking for a site inside the U.S. to hold military commissions, while looking to transfer detainees outside of the prison camp once again.

He said the administration was lifting a moratorium on prisoner transfers to Yemen. It was a proposal Sen. Kelly Ayotte, R-N.H., called "very troubling," suggesting the conditions in Yemen have not improved.

"Nothing has changed," she said in a press conference after the speech.

Congress, though, would still have to back Obama's call to move other detainees to U.S. prisons if the prison is to close.

In re-affirming his pledge to close the detention center at Guantanamo, Obama is pushing for a renewed effort to transfer its 166 detainees to other countries. Congress and the White House have sparred since Obama took office in 2009 over the fate of the suspects and whether they can be brought to trial on U.S. soil. In the meantime, the detainees have been held for years with diminishing hope that they will charged with a crime or be given a trial.

Rep. Buck McKeon, R-Calif., chairman of the House Armed Services Committee, said Thursday he's "open" to a presidential proposal on Guantanamo Bay but called for more than "talking points."

"This speech was only necessary due to a deeply inconsistent counter-terrorism policy, one that maintains it is more humane to kill a terrorist with a drone, than detain and interrogate him at Guantanamo Bay," he said in a statement, asking how the president would handle terrorists too dangerous to release but who cannot be tried.

"Podium platitudes cannot make up for solid answers to these questions," he said.

This week, the Pentagon asked Congress for more than $450 million for maintaining and upgrading the Guantanamo prison. More than 100 of the prisoners have launched a hunger strike to protest their indefinite detention, and the military earlier this month was force-feeding 30 of them to keep them from starving to death.

On drones, Obama defended the decision to order a strike on U.S. citizen Anwar al-Awlaki in Yemen. "He was continuously trying to kill people," Obama said of the Al Qaeda operative.

Addressing recent questions about the scope of U.S. drone authority, Obama also said: "For the record, I do not believe it would be constitutional for the government to target and kill any U.S. citizen -- with a drone, or with a shotgun -- without due process. Nor should any president deploy armed drones over U.S. soil."

Sen. Rand Paul, R-Ky., one of the chief critics of the drone program, said after the speech he was "glad" the president acknowledged the need for due process for potential American targets.

"But I still have concerns over whether flash cards and PowerPoint presentations represent due process; my preference would be to try accused U.S. citizens for treason in a court of law," he said.

Obama acknowledged the civilian deaths that sometimes result -- a consequence that has angered many of the countries where the U.S. seeks to combat extremism -- and said he grapples with that trade-off.

"For me, and those in my chain of command, these deaths will haunt us as long as we live," he said. Before any strike, he said, "there must be near-certainty that no civilians will be killed or injured -- the highest standard we can set."

Ahead of the address, Obama signed new "presidential policy guidelines" aimed at illustrating more clearly to Congress and the public the standards the U.S. applies before carrying out drone attacks. Officials said the guidelines include not using strikes when the targeted people can be captured, either by the U.S. or a foreign government,  relying on drones only when the target poses an "imminent" threat and establishing a preference for giving the military control of the drone program.

However, the CIA is still expected to maintain control of the drone program in Yemen, as well as in Pakistan's tribal areas, given the concern that Al Qaeda may return in greater numbers as U.S. troops draw down in Afghanistan. The military and the CIA currently work side by side in Yemen, with the CIA flying its drones over the northern region out of a covert base in Saudi Arabia, and the military flying its unmanned aerial vehicles from Djibouti.

In Pakistan alone, up to 3,336 people have been killed by the unmanned aircraft since 2003, according to the New America Foundation which maintains a database of the strikes.

The Associated Press contributed to this report.