WASHINGTON – In a shift with profound implications, the Bush administration is attempting to re-energize its terrorism-fighting war efforts in Afghanistan, the original target of a post-Sept. 11 offensive. The U.S. also is refocusing on Pakistan, where al-Qaida is posing fresh threats.

Privately, some senior U.S. military commanders say Pakistan’s tribal areas are at the center of the fight against Islamic extremism; more so than Iraq, or even Afghanistan. These areas border on eastern Afghanistan and provide haven for al-Qaida and Taliban fighters to regroup, rearm and reorganize.

At a Pentagon news conference last week, Defense Secretary Robert Gates said that while the U.S. respects the Pakistani government’s right to decide what actions are needed to defeat extremists on its soil, there are reasons to worry that al-Qaida poses more than an internal threat to Pakistan.

“I think we are all concerned about the re-establishment of al-Qaida safe havens in the border area,” Gates said. “I think it would be unrealistic to assume that all of the planning that they’re doing is focused strictly on Pakistan. So I think that that is a continuing threat to Europe as well as to us.”

In recent days, administration officials have said they would send more U.S. forces, including small numbers of combat troops, if the Pakistani government decided it wanted to collaborate more closely.

It is far from certain that U.S. combat troops will set foot in Pakistan in any substantial numbers. On Friday, Pakistan’s president, Pervez Musharraf, said his country opposes any foreign forces on its soil.