US President Barack Obama had authorised Navy SEAL commandos, on mission to capture or kill al-Qaeda chief Osama bin Laden, to engage the Pakistani police or forces if confronted while carrying out the operation.

As against the wishes of some of his advisors, President Obama insisted to increase the size of his combat team so as that they would be able to successfully handle the Pakistani forces if confronted during the mission, The New York Times has reported.

Pakistan has already said it had scrambled its jets and forces to tackle the foreign forces at Abbottabad, but the US Special Forces left the compound after successfully carrying out the operation in about 40 minutes.

"As the Abbottabad episode illustrates our military responded to the US Forces covert incursion. The Air Force was ordered to scramble. Ground units arrived at the scene quickly. Our response demonstrates that our armed forces reacted, as was expected of them," Pakistan Prime Minister Yousuf Raza Gilani told Parliament yesterday.

The New York Times said Obama's decision to increase the size of the force sent into Pakistan shows that he was willing to risk a military confrontation with a close ally in order to capture or kill the leader of al-Qaeda.

"Such a fight would have set off an even larger breach with the Pakistanis than has taken place since officials in Islamabad learned that helicopters filled with members of a Navy SEAL team had flown undetected into one of their cities, and burst into a compound where bin Laden was hiding," it said.

"Their instructions were to avoid any confrontation if at all possible. But if they had to return fire to get out, they were authorised to do it," a senior Obama Administration official was quoted as saying.

"The planning also illustrates how little the administration trusted the Pakistanis as they set up their operation. They also rejected a proposal to bring the Pakistanis in on the mission," the newspaper reported.

While two helicopters were sent to Abbottabad, under the original plan, two assault helicopters were going to stay on the Afghanistan side of the border waiting for a call if they were needed. But the aircraft would have been about 90 minutes away from the bin Laden compound, it said.

"Some people may have assumed we could talk our way out of a jam, but given our difficult relationship with Pakistan right now, the President did not want to leave anything to chance," one senior administration official was quoted as saying.

"He wanted extra forces if they were necessary," the official added.

If a confrontation appeared imminent, there were contingency plans for senior American officials, including Admiral Mike Mullen, Chairman of the Joint Chiefs of Staff, to call their Pakistani counterparts to avert an armed clash.

But when he reviewed the plans about 10 days before the raid, Obama voiced concern that this was not enough to protect the troops on the mission, administration officials said, according to the newspaper. That resulted in the decision to send two more helicopters carrying additional troops. These followed the two lead Black Hawk helicopters that carried the actual assault team.

While there was no confrontation with the Pakistanis, one of those backup helicopters was ultimately brought in to the scene of the raid when a Black Hawk was damaged while making a hard landing.

The New York Times said two teams of specialists were on standby during the entire operation: One to bury bin Laden if he was killed, and a second composed of lawyers, interrogators and translators in case he was captured alive.

"That team was set to meet aboard a Navy ship, most likely the aircraft carrier Carl Vinson in the North Arabian Sea," the daily said.

With tensions between the US and Pakistan escalating since the raid, American officials yesterday sought to tap down the divisions and pointed to some encouraging developments, the paper said.

It quoted a US official as saying that American investigators would soon be allowed to interview bin Laden's three widows, now being held by Pakistani authorities, a demand that Obama's national security adviser Thomas Donilon made on television last week.