U.S. commanders appear to have concluded that Osama bin Laden is moving among mountain hideouts along a 250-mile stretch of the border between Afghanistan and Pakistan, The New York Times reported on Wednesday. The newspaper cites some American officers as saying the assumption driving the manhunt is that the al Qaeda leader and his top lieutenant, Ayman al Zawahiri, are alive. The unidentified sources cited Afghan and Pakistani intelligence reports that have spoken of bin Laden and an entourage of several dozen moving more than once since the American bombing of the Tora Bora mountains late last year, the Times reported.

Some of those reports have suggested that the fugitives may have moved through the mountains on horseback, probably on cloudy nights to elude aerial surveillance, the newspaper said.

The region being searched covers four provinces -- Kunar, Nangahar, Paktika and Paktia -- and the adjoining Pakistani tribal areas, where suspicions of outsiders run high.

A spokesman for the U.S. command, Lt. Col. Roger King, said Special Forces units in the region aimed to apply pressure on possible hideouts to keep al Qaeda on the run.

"I'd say it's a reasonable conclusion that we feel that if bin Laden is alive, we're providing enough pressure to make sure he keeps moving," King told the Times. "It's easier to spot a moving target."

In public, U.S. officials have for months been unable to confirm or deny that the al Qaeda leaders, blamed by the Washington for the Sept. 11 attacks, are alive.

AL QAEDA DEPUTIES REPORTED IN IRAN

The Washington Post reported Wednesday that two al Qaeda deputies are being harbored by Iran along with dozens of al Qaeda fighters and are said to be plotting new attacks, quoting unidentified Arab intelligence sources.

The newspaper quoted the sources as saying that Saif al-Adel, an Egyptian on the FBI's most-wanted list, and Mahfouz Ould Walid, whom the Pentagon said had been killed in Afghanistan in January -- had moved up the network's hierarchy in recent months.

The Jiddah, Saudi Arabia-datelined story cited Arab intelligence sources outside Saudi Arabia who did not want their countries disclosed.

The report said al-Adel, Walid and dozens of other al Qaeda members were staying in hotels and guesthouses in the Iranian border cities of Mashhad and Zabol.

"There is an Iranian role in hosting al Qaeda and sponsoring the movement of al Qaeda," a senior Arab intelligence officer told the Post.

With Osama bin Laden and his chief lieutenants in hiding or dead, al-Adel an Walid have assumed operational control of al Qaeda's military committee, which directs attacks, the sources were quoted as saying.

Al-Adel, head of al Qaeda's security committee, was indicted in the United States on murder and conspiracy charges in the 1998 U.S. Embassy bombings in Tanzania and Kenya.

Walid, a longtime bin Laden lieutenant, has played a role in developing the doctrine to justify al Qaeda attacks. The Post quoted its sources as saying Walid had assumed control of al Qaeda's religious committee and, because he is in Iran with al-Adel, was also participating in military planning.

A spokesman for the Iranian mission to the United Nations denied that the two men were in Iran, the paper said.

"Iran's policy is not to permit such people to enter Iran," the Iranian official said.

However, the Post quotes its sources as saying that al-Adel and Walid meet regularly with lieutenants in Mashhad and Zabol.

The intelligence officers said al Qaeda had planned attacks in Europe, Africa, the Middle East and the Gulf this year and also planned to kill Americans on the streets of Saudi Arabia, the newspaper reported.

PHOTO CAPION

Osama bin Laden is shown in an undated video grab released in October 2001. An Arab journalist in London said on August 27 that bin Laden is still firmly in control of al Qaeda, blamed for the September 11 attacks on the United States. REUTERS