US officials were concerned that Pakistan could jeopardise the Osama bin Laden operation and "might alert the targets," if Islamabad took part in the mission, Leon Panetta, the CIA director, has said.
In an interview with Time magazine published on Tuesday, Panetta said the CIA had ruled out working with Pakistan on the raid because "it was decided that any effort to work with the Pakistanis could jeopardize the mission: They might alert the targets".
He said his aides had 60 to 80 per cent confidence that bin Laden was in the compound in Abbottabad, a town about two hours north of Islamabad, the capital.
Pakistan on Tuesday denied any prior knowledge of the US raid that killed bin Laden, but said it had been sharing information about the targeted compound with the CIA since 2009.
While Islamabad hailed the killing of bin Laden as an important milestone in the fight against terrorism, the foreign ministry said Pakistan had expressed "deep concerns" that the operation was carried out without informing it in advance.
"Neither any base nor facility inside Pakistan was used by the US forces, nor the Pakistan Army provided any operational or logistic assistance to these operations conducted by the US forces," the ministry said in a lengthy statement.
"This event of unauthorised unilateral action cannot be taken as a rule."
The statement said US helicopters entered Pakistani airspace by making use of "blind spots" in the radar coverage caused by the hilly terrain surrounding Abbottabad.
The foreign ministry said the Pakistani air force scrambled its planes within minutes of being informed of the US operation, but there was no engagement with the US forces as they had already left Pakistani airspace.
It said Pakistan's Inter Services Intelligence (ISI) spy agency had been sharing information about the compound with the CIA and other friendly intelligence agencies since 2009, and had continued to do so until mid-April.
"It is important to highlight that taking advantage of much superior and technological assets, CIA exploited the intelligence leads given by us to identify and reach Osama bin Laden," the statement said.
Hamid Gul, the former Chief of the ISI, told Al Jazeera that excluding the security agency from the operation demonstrated that the US had no intention of capturing Bin Laden alive.
"The main reason I suspect, is that they did not want him alive ... if the ISI had been tipped off, the ISI would have gone and captured him and would have presented him for trial or something like that.
"Many untold stories would have come out ... they sneaked in and carried out a raid, which is an act of war actually," Gul said.
Asif Ali Zardari, the president of Pakistan, has also emphasied that the killing of bin Laden by US forces was not a joint operation with his country.
|Zardari said the whereabouts of bin Laden was not known to the Pakistani authorities [GALLO/GETTY]
In an opinion column published in the Washington Post, a US newspaper, Zardari said the whereabouts of the al-Qaeda leader was not known to the Pakistani authorities.
Zardari also denied suggestions that the ISI may have sheltered bin Laden before he was killed by US forces.
"He was not anywhere we had anticipated he would be, but now he is gone," he wrote.
"Although the events of Sunday were not a joint operation, a decade of co-operation and partnership between the United States and Pakistan led up to the elimination of Osama bin Laden as a continuing threat to the civilised world," Zardari said.
Sohail Rahman, Al Jazeera's correspondent in Islamabad, said: "Since the operation ... the strains and stresses between both the United States and Pakistan have been quite evident.
"When you have officials such as the president saying he didn't know anything about it, juxtaposed with the prime minister, Yousuf Raza Gillani, saying 'yes we did know', then that confuses the masses here in a country that is already very angry about issues such as [US] drone attacks ... on their territory.
"The ISI ... gives the impression that they know everything that is going on in the country and therefore when you have an agency turning round, along with the military, and then the civilian government, saying 'we knew nothing', questions are being raised."
'Sympathetic towards Islamists'
Bin Laden was killed in a raid by US forces on a large house close to a military academy in the bustling town of Abbottabad, not in the remote Afghan border region where many had assumed he had been holed up.
That was quickly taken as a sign of possible collusion with Pakistan's powerful security establishment, which Western officials have long regarded with a measure of suspicion despite several notable al-Qaeda arrests in the country since 2001.
"Some in the US press have suggested that Pakistan lacked vitality in its pursuit of terrorism, or worse yet that we were disingenuous and actually protected the terrorists we claimed to be pursuing.
"Such baseless speculation may make exciting cable news, but it doesn't reflect fact," Zardari wrote.
Speaking to Al Jazeera on Tuesday, Robert Fisk, a journalist with the Independent, a UK newspaper, who has previously interviewed bin Laden, said that people shoud stop talking about the ISI as if it was a single entity.
He said: "They're [the ISI] not all one unique institution, they are differing in their views, some of them are pro-American, some of them are very anti-American, some of them are clearly sympathetic towards Islamists, extremists, whatever you like to call them.
"I called up one of the men I know last night and put it to him, 'look, you know, this house was very big, come on, you must have have had some idea.'
"What he said to me was 'sometimes it's better to survey people than to attack them.'
"And I think what he meant was that as long as they knew where he [bin Laden] was, it was much better to just watch rather than stage a military operation that may bring about more outrages, terrorism, whatever you like to call it."