WASHINGTON?In a potential blow to the U.S. war effort, Pakistan appears to be preparing to pull troops away from the Afghan border area, U.S. defense officials said Tuesday.

The Pakistani military presence along the Afghan border has been a key element of the U.S. strategy for hunting down and capturing or killing Taliban and al Qaeda fighters who slipped across the border. Without Pakistan’s help, the United States has little short-term prospect of finishing off al Qaeda. we need as much assistance as possible in guarding that very porous border,” Victoria Clarke, chief spokeswoman for Defense Secretary Donald H. Rumsfeld, told reporters.

Pakistan said last week that it might remove troops from the Pakistan-Afghanistan border region, where they are helping the United States search for al Qaeda and Taliban, and move them toward Kashmir because of the escalating conflict there.

U.S. officials have been talking with both sides because of what Clarke called “grave” concern that the India-Pakistan dispute could escalate into all-out war, or even a nuclear exchange.