"I think it's inconceivable that bin Laden did not have a support system in the country that allowed him to remain there for an extended period of time," Deputy National Security Advisor for Counter-terrorism and Homeland Security John Brennan told reporters at a crowded White House news conference.
"I am not going to speculate about what type of support he might have had on an official basis inside of Pakistan," he said.
Bin Laden was shot dead yesterday in a pre-dawn helicopter-borne secret US operation in a house just yards away from Pakistan's Military Academy in Abbottabad, raising questions whether the establishment knowingly harboured him.
"We are closely talking to the Pakistanis right now. And, again, we are leaving open opportunities to continue to pursue whatever leads might be out there," Brennan said responding to questions on how the most wanted terrorist was found in one of the most affluent neighborhoods of Islamabad, which is residences of top retired military officials.
"People have been referring to this as hiding in plain sight. Clearly, this was something that was considered as a possibility. Pakistan is a large country. We are looking right now at how he was able to hold out there for so long and whether or not there was any type of support system within Pakistan that allowed him to stay there," Brennan said.
"We know that the people at the compound there were working on his behalf, and that's how we ultimately found our way to the compound. But we are right now less than 24 hours after this operation, so we are talking with the Pakistanis on a regular basis now. And we're going to pursue all leads to find out exactly what type of support system and benefactors that bin Laden might have had," he said.
Brennan said following the conclusion of the successful operation, a number of senior US officials are in regular contact now with their Pakistani counterparts.
"We are continuing to engage with them. We're engaging with them today as we learn more about the compound and whatever type of support system bin Laden had."
Brennan said the fact that bin Laden was found so close to the capital "raises questions".
"There are a lot of people within the Pakistani government, and I'm not going to speculate about who or if any of them had fore-knowledge about bin Laden being in Abbottabad. But certainly his location there outside of the capital raises questions. We are talking to the Pakistanis about this," he said.
"But they, at least in our discussions with them, seem as surprised as we were initially that bin Laden was holding out in that area," he added.
Brennan said the US troops were prepared to capture bin Laden alive, but his resistance and use of a woman, presumed to be his wife, as shield forced them to kill him.
"If we had the opportunity to take bin Laden alive, if he didn't present any threat, the individuals involved were able and prepared to do that. We had discussed that extensively in a number of meetings in the White House and with the (US) President," he said.
"We were not going to put our people at risk. The president put a premium on making sure that our personnel were protected, and we were not going to give bin Laden or any of his cohorts the opportunity to carry out lethal fire on our forces. He was engaged, and he was killed in the process. But if we had the opportunity to take him alive, we would have done that," he said.
Brennan said the course of action and the subsequent decisions were made over the course of the last several months.
"There was a working group that was working this on a regular basis, if not a daily basis, over the last several weeks, looking at every decision and based on what type of scenario would unfold, what actions and decisions would be made," the official said.
"It was looked at from the standpoint of, if we captured him, what would we do with him, where would he go. If he was killed, what would we do with him and where would he go?" he added.
Besides bin Laden, the two Al Qaeda facilitators - who were the courier, his son Khalid and a woman presumed to be his wife, died in the operations.
"She served as a shield; again, this is my understanding. And we're still getting the reports of exactly what happened at particular moments. "She fought back when there was an opportunity to get to bin Laden; she was positioned in a way that indicated that she was being used as a shield, whether or not bin Laden or the son or whatever put her there or she put herself there," the White House official said.
"That's again my understanding, that she met her demise, and my understanding is that she was one of bin Laden's wives," he added.
Brennan also said that burial at sea was the "best option" available for bin Laden.
He said it was decided much in advance that in the "best interests of all involved that this burial take place, again, according to Islamic requirements, at sea."