NEW YORK, Aug 2: US commanders of the raid on Osama bin Laden considered a more down-to-earth way of entering his compound than swooping in by helicopter, a report said on Monday. Tunnelling.

The short-lived idea would have avoided ground troops having to sneak through the nearby town of Abbottabad as they penetrated the walled house where the Al Qaeda leader was hiding, The New Yorker reported.

Planners also had to consider the possibility that their quarry might himself have tunnels ready for an escape.

In the end, though, they determined from satellite photos that the water table was probably just below the surface of the surrounding flat land and that tunnelling was highly unlikely to be successful.

A less exotic option for striking Bin Laden was to bomb from the sky. The New Yorker article detailed how then secretary of defence Robert Gates preferred a strike by B-2 Spirit bombers to sending in troops.

However, to be sure of destroying the house and any fortified bunker underneath would require such a massive bombardment that it would result in Abbottabad feeling “the equivalent of an earthquake”, James Cartwright, the then vice-chairman of the joint chiefs of staff, told The New Yorker.

President Barack Obama disliked that idea and said the helicopter raid should go ahead.

The spectacular incursion by the United States into a supposedly allied country's territory and the row over Bin Laden's long-time presence there triggered a crisis in US-Pakistani relations.

However, the raid, dubbed Operation Neptune’s Spear, was not the first into Pakistan, The New Yorker article said.

Commandos had already been sent up to 12 times into Pakistan on previous occasions, the magazine quoted a special-operations officer close to the Bin Laden raid as saying. Most missions were into North and South Waziristan.

Once the plan was decided on, a top priority was to keep it secret from Pakistan.

“There was a real lack of confidence that the Pakistanis could keep this secret for more than a nanosecond,” a senior adviser to Obama told the magazine.—AFP