The United States aims to build upon its killing of Osama bin Laden to destroy his al Qaida terrorist organisation, the White House counterterrorism chief has said.
John Brennan declared the administration was determined to "pummel the rest of al Qaida" as the US moves on from the daring Navy Seal raid that eliminated bin Laden in a surprise attack on his compound not far from Islamabad, the Pakistan capital.
Mr Brennan said the feared and expanding al Qaida organisation had suffered "severe body blows" during the 10-year US-led war in Afghanistan.
US President Barack Obama, who gave the final orders for the raid on Sunday, has vowed to begin withdrawing some American forces from Afghanistan this summer.
Mr Obama plans to visit the site of the former World Trade Centre in New York on Thursday to mark the killing of bin Laden and remember the nearly 3,000 who were killed in the Twin Towers and the Pentagon on September 11, 2001.
The United States, under then-President George Bush, invaded Afghanistan later that year hoping to eliminate the al Qaida sanctuary provided by the militant Taliban government then controlling the country.
Bin Laden and his top lieutenants were believed to have fled to neighbouring Pakistan as US forces swept the Taliban from power.
Until Sunday, however, bin Laden had escaped reckoning for the attacks on the World Trade Centre in New York and the Pentagon. Passengers on the fourth jet fought al Qaida hijackers but were killed as the aircraft then plunged to the ground in Pennsylvania.
In an appearance on NBC television, Mr Brennan said "clearly there was some kind of support network" for bin Laden inside Pakistan. He declined to blame the Pakistani government for that, calling Islamabad "a strong counterterrorism partner."
But he also said the Pakistani government is conducting its own investigation into how bin Laden dodged authorities for so long. Mr Brennan said it is "unknown at this point" whether individuals inside the Pakistani government were helping bin Laden.