ISLAMABAD, 23 February 2004 — Pakistan has stepped up security near its rugged border with Afghanistan ahead of a fresh operation aimed at cornering Al-Qaeda and Taleban holdouts in the tribal belt where Osama Bin Laden also may be hiding, military and intelligence sources said yesterday.

The operation will be the fourth of its kind since the Sept. 11, 2001, attacks in the United States, said the Pakistani security sources, who spoke on condition of anonymity. It will center on suspected Taleban and Al-Qaeda men who authorities believe have married Pakistani women and are living in the tribal areas - the remote and historically autonomous regions that have never really been brought under the control of Pakistan's central government.

It will be conducted in the Waziristan tribal region in Pakistan's Northwest Frontier Province, Pakistani intelligence sources said. Bin Laden was not the immediate target of the operation, said one senior intelligence official. But he said the hope was that the operation would net clues that would ultimately lead to the "biggest evil."

"Right now, we are not chasing Bin Laden, but the purpose of all past efforts was to capture him," he said. "We are now tracking Al-Qaeda fugitives to get clues from them about him." Gen. Shaukat Sultan, the army spokesman, also said the operation's purpose was to capture terrorists in general - not Bin Laden in particular. "It is an ongoing effort, and not aimed at capturing any specific person," he said yesterday.

Security was stepped up in the tribal region so that no one could escape arrest, military sources said. The operation comes amid rising speculation in the local press that the US military is planning a spring offensive in Afghanistan to capture Bin Laden.

Many of the reports have speculated that the operation would spill over into Pakistani border areas, where the inhabitants are linked by language and culture to Afghan Pashtuns, the ethnic group that was the Taleban's power base.

Pakistan has been a key ally of the United States in its war on terror, and Pakistani security forces have captured more than 500 suspected Al-Qaeda and Taleban fugitives since the attacks on the World Trade Center and the Pentagon. Among the captured are key figures in Bin Laden's terrorist network.

Earlier this week, the top American general in Afghanistan, Lt. Gen. David Barno, said he hoped that efforts by Pakistan, together with a change in US tactics in Afghanistan, would create a "hammer-and-anvil" effect along the mountainous border area - to trap Al-Qaeda fighters between US and Pakistani forces.

Pakistani soldiers and government paramilitaries have been meeting with tribal chiefs for at least six weeks and threatening them with "destruction of homes and things of that nature" unless they cooperate, Barno said. A deadline has been given to tribal elders to surrender these people to the army. Authorities have promised that they will not be extradited if they surrender and hand in their weapons.

The planned operation in Waziristan mirrors earlier ones. The first took place in Wana, a remote border tribal region, in June 2002. It failed to net any major Al-Qaeda leader but several Pakistani soldiers died.

The army again sent troops to the same region in October 2003 in an effort to arrest Bin Laden's top associates. A similar operation was again conducted in January during which Ahmad Said Al-Kadr, a suspected Al-Qaeda financier, was killed along with seven other suspects.