Washington ? Osama bin Laden is hiding in a remote tribal area along Afghanistan’s 1,500-mile border with Pakistan, separated from his top deputy and, in a sign he has to be careful about whom he trusts, surrounded by fellow Arabs.

His No. 2, Ayman al-Zawahri, is hiding in a more settled area along the border, surrounded by al-Qaida operatives of his Egyptian nationality, according to U.S. intelligence officials familiar with his pursuit.

Their separation has opened a debate in national security circles in the United States and elsewhere about whether the leaders have split up. Neither man mentions the other by name in public pronouncements, and both headed separate groups before joining forces in 1998.

Al-Zawahri has decided to take a more prominent public role than has bin Laden, releasing dozens of written and recorded Internet messages, including a video this month urging Muslims to support Iraqi insurgents.

On Sunday, bin Laden was heard in his first new message in three months, purportedly saying the West was at war with Islam and calling on his followers to go to Sudan to fight a proposed U.N. force in Darfur.

U.S. and Saudi officials, several of whom spoke on condition of anonymity because of the information’s sensitive nature, say the al-Qaida leaders have made a strategic security decision to hide in different places from one another. These officials do not yet see evidence of an ideological split.

“I don’t think they have the luxury to have a rift,” said Jamal Khashoggi, an adviser to the Saudi ambassador to Washington, Prince Turki al-Faisal. A former reporter and editor, Khashoggi interviewed and traveled with bin Laden at times between 1987 and 1995. Bin Laden lost his Saudi citizenship in 1994 after governments in Algeria, Egypt and Yemen accused him of financing subversion.

Tracking bin Laden

Bin Laden’s at-large status has hounded the Bush administration. When people were asked in a recent CNN-USA Today-Gallup poll if bin Laden will be killed or captured in 2006, only 27 percent said yes, while 68 percent said no.

In a position paper released late last month, congressional Democrats pledged to “eliminate” bin Laden by doubling the number of special forces and adding more intelligence operatives.

A senior Pakistani security official said Pakistani security forces working closely with the CIA came close to capturing bin Laden a couple years ago, missing by a few hours. Clues to his whereabouts have dried up.

The official, who spoke on condition of anonymity because he is not authorized to speak to media, said bin Laden and some associates were hiding in Waziristan, near the Afghan border, at the time. The official would not elaborate on who those associates were or who had sheltered the al-Qaida leader.

It is unclear now where bin Laden and al-Zawahri are.

Some U.S. officials believe they are hiding on the Pakistani side of the border with Afghanistan, protected by tribes that warn when Pakistani forces may be approaching, several U.S. counterterrorism officials said.

The Pakistani government does not believe that is true.

Interior Minister Aftab Khan Sherpao told The Associated Press that he has no information suggesting that the al-Qaida leaders are in Pakistan. “Naturally, we can’t go on a wild goose chase. We can only act if we get credible information about the hideout. … We have got no evidence,” he said.

He and others believe bin Laden and al-Zawahri may be on the Afghan side of the border, perhaps in rugged, autonomous Kunar. One of 34 provinces in Afghanistan, Kunar is slightly smaller than Delaware.

Perfect for hiding

No matter which side, the border gets little respect, particularly compared with deep-seated tribal and family loyalties. Complicating the search, the mountainous region – with peaks taller than the Rockies – is full of centuries-old routes used for trade, smuggling and invasions that would be invaluable for evading capture.

Parts of the Afghan side are controlled by renegade Islamic militia leader Gulbuddin Hekmatyar, who Khashoggi and others say may be allied with bin Laden and al-Zawahri.

“They don’t have many choices to hide in Afghanistan,” Khashoggi said. “I think they are roaming in a very limited area.”

The marriage would be one of convenience, centered largely on a mutual disdain for the United States. After the U.S. invasion of Afghanistan in 2001, U.S. officials began to suspect Hekmatyar was aligning himself with al-Qaida. The CIA tried to kill him with a Predator drone in May 2002.

Help from Hekmatyar would be invaluable, given that bin Laden and al-Zawahri are foreigners and do not speak the languages native to the region. Joining the U.S. in any searches on the Afghan side are thousands of NATO troops from countries including Britain, Canada and the Netherlands.

Information on al-Zawahri

Intelligence officials got some confirmation that al-Zawahri is surrounded by only the closest of associates with the Jan. 13 Predator drone attack on a house in Damadola, just across from Kunar.

U.S. officials will not confirm that the strike happened, and Pakistani officials suspect at least four foreign militants died in the strike. The list includes Egyptian Midhat Mursi, an explosives and chemical weapons expert; Abu Obaidah al-Masri, a chief responsible for attacks on U.S. forces in eastern Afghanistan; and Al-Abdul Rehman al-Maghribi, al-Zawahri’s Moroccan son-in-law. Mursi had a $5 million bounty on his head and is on the FBI’s list of most-wanted terrorists.

Authorities hoped al-Zawahri would be at the high-level dinner called Eid al-Adha, marking the end of Muslims’ pilgrimage to Mecca.

The fact that the U.S. could target the gathering signaled to some security experts that someone in the region betrayed the al-Qaida leader – and the U.S. was able to take advantage of the fissure.

“For the United States to get wind of a high-level dinner like that and have precise information on when it is taking place, someone must have betrayed somebody – absolutely,” said Ken Katzman, an expert on terrorism at the Congressional Research Service who recently traveled to Afghanistan.

U.S. intelligence officials believe bin Laden and al-Zawahri are surrounded by smaller entourages of perhaps 10 or 20 people. Katzman called it a “fairly sculpted group” of “close cronies” – often of their own country. “If you are an Egyptian in that region, Zawahri is your mentor and the one you look up to more,” he said.

Counterterrorism officials say Egyptians in the region play an important role in protecting the al-Qaida leaders.