WASHINGTON - UNDER growing pressure from US missile strikes, the al-Qaeda terror network is relying more heavily on local insurgent groups along the Pakistan border to house training camps that are growing smaller and more mobile, according to counterterrorism officials and analysts.

The changes in the terror group's training operations - often hidden inside walled compounds deep in Pakistan's mountains - have made them increasingly difficult to target by US intelligence forces as they have stepped up drone attacks over the past year.

While the training still includes forays into deserted hillsides to practice planting and detonating explosives, al-Qaeda trainers are now also taking their instruction on the road, moving temporary training operations from compound to compound, where fellow insurgents welcome them.

The attacks on the camps, which have become an integral part of the Obama administration's war against the terror group, also risk civilian casualties - which in turn have inflamed anti-American sentiment among the Pakistanis, critical allies in widening the anti-terror campaign.

The camps took on a heightened profile in recent months as US investigators probed the case of accused New York terror suspect Najibullah Zazi. The Afghan emigre reportedly flew to Pakistan late last year and traveled to Peshawar, in the northwest frontier, where he received training on weapons and explosives.

Counterterrorism officials estimate that Zazi is one of 100 to 150 westerners who have gone to the Pakistan border region for terror training in the last year. Their ability to filter in and out of the isolated camps has fueled fears that 'sleeper' operatives bearing US or western passports are traveling back and forth with ease to train and plot attacks destined within America's borders. -- AP