U.S. President Barack Obama said on Sunday that al-Qaida leader Osama bin Laden likely had support within Pakistan, but the nature of that support is not yet known.
"We think that there had to be some sort of support network for Bin Laden inside of Pakistan. But we don't know who or what that support network was," he said in excerpts of an interview with CBS to air Sunday evening.
He said the Pakistani government had indicated that it had "a profound interest in finding out what kinds of support networks bin Laden might have had."
Despite the U.S. president's statements, an Obama administration official said earlier on Sunday that they have seen no evidence that the Pakistani government knew bin Laden was living in the country before his killing.
"I can tell you directly that - I've not seen evidence that would tell us that the political, the military, or the intelligence leadership had foreknowledge - of bin Laden," U.S. National Security Adviser Tom Donilon told NBC's "Meet the Press" when asked if Pakistan was guilty of harboring the al Qaeda leader.
But he added bin Laden's residence for several years inside a compound in Abbottabad, 35 miles north of the capital, Islamabad, "needs to be investigated."
"The Pakistanis have said they're going to investigate," Donilon said. "This is a very big issue in Pakistan right now. How could this have happened in Pakistan? We need to investigate it. We need to work with the Pakistanis. And we're pressing the Pakistanis on this investigation."
He said Pakistani officials also needed to provide U.S authorities with intelligence they had gathered from the compound where bin Laden was killed, including access to three wives who are in Pakistani custody.
But he added that despite difficulties in the U.S.-Pakistani relationship, "We've also had to work very closely with Pakistan in our counter-terror efforts. More terrorists and extremists have been captured or killed in Pakistan than anyplace else."
Pakistan, heavily dependent on billions of dollars in U.S. aid, is under intense pressure to explain how bin Laden could have spent so many years undetected just a few hours' drive from its intelligence headquarters in the capital.
Senior Pakistani officials said on Saturday that bin Laden may have lived in Pakistan for more than seven years before he was shot to death by U.S. Navy SEALs.
One of bin Laden's widows told Pakistani investigators that he stayed in a village for nearly 2 1/2 years before moving to the nearby garrison town of Abbottabad.
The wife, Amal Ahmed Abdulfattah, said bin Laden and his family had spent five years in Abbottabad, where one of the most elaborate manhunts in history ended on Monday.
Suspicions have deepened that Pakistan's pervasive Inter-Services Intelligence spy agency, which has a long history of contacts with militant groups, may have had ties with bin Laden -- or that at least some of its agents did. The agency has been described as a state within a state.
Pakistan has dismissed such suggestions and says it has paid the highest price in human life and money supporting the U.S. war on militancy launched after bin Laden's followers staged the September 11, 2001, attacks on the United States.
Donilon said the killing of bin Laden was "a real blow" to the al-Qaida militant network.
He said an administration assessment at the end of last year determined that al-Qaida was in its weakest shape since 2001, although still dangerous.
"With the steps that we took with the assault on the compound in Pakistan and the killing of Osama bin Laden, they are even weaker still," he said.
Donilon declined to discuss if evidence uncovered at bin Laden's compound revealed evidence of specific al-Qaida plots against the United States, but said, "It's absolutely critical for us to remain vigilant as we continue to press this organization."