WASHINGTON, Feb. 18 — Senior leaders of Al Qaeda operating from Pakistan have re-established significant control over their once-battered worldwide terror network and over the past year have set up a band of training camps in the tribal regions near the Afghan border, according to American intelligence and counterterrorism officials.

American officials said there was mounting evidence that Osama bin Laden and his deputy, Ayman al-Zawahri, had been steadily building an operations hub in the mountainous Pakistani tribal area of North Waziristan. Until recently, the Bush administration had described Mr. bin Laden and Mr. Zawahri as detached from their followers and cut off from operational control of Al Qaeda.

The United States has also identified several new Qaeda compounds in North Waziristan, including one that officials said might be training operatives for strikes against targets beyond Afghanistan.

American analysts said recent intelligence showed that the compounds functioned under a loose command structure and were operated by groups of Arab, Pakistani and Afghan militants allied with Al Qaeda. They receive guidance from their commanders and Mr. Zawahri, the analysts said. Mr. bin Laden, who has long played less of an operational role, appears to have little direct involvement.