Powell, who was scheduled to leave Washington yesterday, makes his first trip to India and Pakistan since July 2002 as the United States has begun a spring offensive in Afghanistan to try to catch the accused Sept. 11, 2001 mastermind.

Given Pakistan's porous border with Afghanistan, the help of Pakistani President Pervez Musharraf is thought vital if the United States is to catch bin Laden and defeat his al-Qaeda network and their former Taliban supporters in the region.

"They want bin Laden and they want Musharraf to survive because they think it's the only chance of getting bin Laden." said Jim Steinberg, a foreign policy analyst and a former deputy national security adviser under US President Bill Clinton.

While pressing Musharraf for every possible assistance in the "war on terror," Powell is also expected to privately seek maximum information on the activities of Abdul Qadeer Khan, the Pakistani scientist who has admitted selling nuclear secrets to Iran, Libya and North Korea but was pardoned by Musharraf.

The United States has chosen not to criticize Khan's pardon partly out of fear that a public trial could implicate many in the Pakistani elite and undermine Musharraf's rule. But it also wants every scrap of information about what Khan did.

"If I were asking ... I would say where did he go, when did he go there, who did he see and what did he share?" said Karl Inderfurth, a former assistant secretary of state for South Asian affairs who expected the issue to be raised in private.

A senior State Department official said Pakistan had already provided some detail on Khan's activities, including revelations that helped in last month's Beijing talks on ending North Korea's suspected atomic weapons programme.

The official also praised Musharraf, who seized power in a bloodless 1999 coup and survived two assassination attempts in December, for having made tough, sometimes unpopular, decisions on fighting the Taliban, starting peace talks with India and exerting some control in the tribal areas near Afghanistan.

"He has bitten the bullet on a lot of very tough issues," said the official. "I guess there is fear by some that he has bitten more bullets than he can chew."

Powell begins his trip in New Delhi, a visit that will allow him to promote the newly revived peace talks between India and Pakistan, which came to the brink of war in 2002, and to extol the budding US-Indian "strategic partnership."