Usama bin Laden (search) and fugitive Taliban chief Mullah Mohammed Omar (search) are thought not to be in Afghanistan, the U.S. Ambassador Zalmay Khalilzad said Thursday, a day after a purported commander of the rebel group said the pair are alive and well.

U.S. officials have repeatedly said the fugitive Al Qaeda (search) leader is thought to be some place in the rugged mountains between Afghanistan and Pakistan.

"Mullah Omar is not in Afghanistan. I do not believe that Usama is in Afghanistan," the U.S. ambassador to Afghanistan told reporters at a press conference in Kabul.

Khalilzad did not say where the two were believed to be hiding.

"It is not an easy job to find one person, maybe with some (people) helping him, ... in a vast region. It requires timely intelligence," he said.

Despite the failure to catch bin Laden since the Sept. 11, 2001, attacks on America, Khalilzad said "a lot of progress" had been made in combatting his terror network. He said it wasn't clear how much operational control bin Laden still had over Al Qaeda.

"Significant numbers of the leaders of Al Qaeda have been captured. Their network has been disrupted ... the financial network has also been disrupted," he said.

He add that it is symbolically very important that bin Laden be brought to justice and "sooner or later I believe firmly that he will be caught."

Pakistani President Gen. Pervez Musharraf (search) said during a visit to Australia this week that his government doesn't "have a clear idea" where bin Laden is hiding. In comments Thursday, he claimed that his security forces have "broken the back" of Al Qaeda in Pakistan.

Khalilzad said catching bin Laden and Omar required the cooperation of several governments, which, he added, should not allow militants to use their territory for "propaganda purposes against Afghanistan."

The comments appeared to be a veiled criticism of Pakistan. On Wednesday, Pakistan's Geo television broadcast an interview with a man it identified as Taliban military commander Mullah Akhtar Usmani, a former Afghan aviation minister, who said bin Laden was "absolutely fine." He would not specify where bin Laden was hiding.

Pakistani officials declined to comment Thursday on Khalizad's remarks.

In the video, a black turban shielded the man's face, making it impossible to recognize him or verify his identity, and an AK-47 rifle was propped next to him as he spoke.

The man said the Taliban (search) are still organized and senior Taliban leaders hold regular consultations. "Our discipline is strong. We have regular meetings. We make programs," he said.

He said Omar does not attend the meetings but "decisions come from his side." He did not say where those meetings take place.

Geo said the interview was recorded last week. A senior journalist at the independent station said the interview was done near the Afghan town of Spinboldak, which is close to the Pakistani border.

In Washington, a U.S. intelligence official said on condition of anonymity that it seemed reasonable to believe that former Taliban officials still gather to meet.

Gen. Zaher Azimi, a spokesman for the Afghan Defense Ministry, said Wednesday that the interview was "not serious" and wouldn't help the rebels. He questioned why the man claiming to be Usmani was afraid to show his face, though he stopped short of questioning his identity.

"He was just saying the same thing as usual," Azimi said. "This doesn't make any difference in terms of improving their military or political situation."

In speaking about Omar, the man referred to the Taliban chief by his self-proclaimed title of "ameerul momineen" — "leader of the faithful."

"Ameerul momineen is our chief and leader. No one is against him. Our ameerul momineen is alive. He is all right. There is no problem. He is not sick. He is my commander. He gives me instructions," the man said.

Asked whether he has direct contact with Omar, the man said: "I will not say whether I meet with him or not. But he is giving instructions."

A U.S.-led coalition ousted the Taliban in late 2001. The offensive was launched after the Taliban refused to hand over bin Laden and dismantle Al Qaeda bases in Afghanistan after the Sept. 11, 2001, terrorist attacks on the United States, which bin Laden is accused of orchestrating.