WASHINGTON - President Bush has approved a plan to intensify the effort to capture or kill Osama bin Laden, senior administration and military officials say, as a combination of better intelligence, improving weather and a refocusing of resources away from Iraq has reinvigorated the hunt along the border between Pakistan and Afghanistan.
The plan will apply both new forces and new tactics to the task, said senior officials in Washington and Afghanistan who were interviewed in recent days. The group at the center of the effort is Task Force 121, the covert commando team of Special Operations forces and Central Intelligence Agency officers. The team was involved in Saddam Hussein's capture and is gradually shifting its forces to Afghanistan to step up the search for bin Laden and Mullah Mohammed Omar, the former Taliban leader.
After a visit to Pakistan this month by the director of central intelligence, George J. Tenet, President Pervez Musharraf of Pakistan appears to be far more seriously committed to tracking down al-Qaida and Taliban militants along the semiautonomous border region, American officials say.
"Two assassination attempts close together tends to be life-focusing," said a senior official overseeing the new drive, referring to the December attacks on Musharraf.
Bin Laden and his deputies have painted Musharraf as a lackey of the United States, and many officials here say they believe that al-Qaida had a role in the assassination attempts. Musharraf has told the United States, the senior official said, that "he is now willing to be even more helpful" in tracking down al-Qaida and Taliban militants in the region where bin Laden is believed to be hiding.
Under the new plan, officials say, the 11,000 American forces in Afghanistan are changing their tactics. Rather than carrying out raids and returning to their bases, small groups will remain in Afghan villages for days at a time, handing out various forms of aid and conducting patrols. By becoming a more permanent, familiar presence, American officials say, they hope to be able to receive and act on intelligence within hours. Such a technique helped them to capture Hussein.
"We're trying to transplant some of the lessons of the Saddam capture," one senior official said. "This is different territory, and our targets are presumed to be moving around. But one lesson we learned in Iraq is that, by analogy, there are only a limited number of places that someone like Saddam or bin Laden feel comfortable."
Similarly, Task Force 121 and the Pakistani forces are focusing on bin Laden's support network, hoping it will crack as Hussein's did.
With a great deal at stake strategically, symbolically and politically, Bush and his national security team have repeatedly met in recent months to refine the new approach, and it appears to have been approved in the past two months. White House officials will not say exactly when, emphasizing that the hunt for bin Laden never stopped, though clearly the effort lost momentum.
Much of the timing is driven by the weather: As winter snows melt, troops can navigate in the high mountain passes and trails where many al-Qaida and Taliban members are believed to be hiding. When that moment arrived last year, many of the forces and American intelligence operatives now engaged in Afghanistan were tied up in Iraq.
But presidential politics are also at play. Though the White House denies that Bush is letting the election influence strategy, some of his aides have privately spoken about the obvious advantages of going into the last months of the election campaign with both Hussein and bin Laden in custody.
On Friday, Sen. John Kerry, a Massachusetts Democrat and the front-runner in the Democratic race, appeared to try to inoculate his campaign from the possibility of bin Laden's capture, while at the same time faulting Bush for failing to put together an effective search strategy far earlier.
"As we speak, night has settled on the mountains of the border between Afghanistan and Pakistan," Kerry said in California. "If Osama bin Laden is sleeping, it is the restless slumber of someone who knows his days are numbered. I don't know if the latest reports - saying that he is surrounded - are true or not. We've heard this news before."
Kerry said, "We had him in our grasp more than two years ago at Tora Bora, but George Bush held U.S. forces back and instead called on Afghan warlords with no loyalty to our cause to finish the job."
Kerry's aides contended that Bush's new strategy was a tacit admission of past failures and said the White House had criticized Kerry for questioning its earlier strategy.
White House and military officials insist that despite the rumors to which Kerry alluded, they do not know bin Laden's whereabouts.
Pentagon and Pakistani officials denied yesterday a report on Iranian state radio that bin Laden had been captured in the region long ago. The report was carried by Iran radio's external Pushtun service, which is designed for listeners in Afghanistan and Pakistan, where the language is widely spoken.
Iran state radio's main news channel - the Farsi-language service for Iranian listeners - did not carry the bin Laden report. Iran state television also did not carry the report.
The radio quoted its reporter as saying that bin Laden had been in custody for a period of time, but that a U.S. announcement of the capture was being withheld by Bush until closer to the November election.
Defense Secretary Donald H. Rumsfeld, speaking to reporters Thursday, sounded testy when asked about the chances of finding bin Laden, saying it "will happen when it happens, and I don't believe it's closer or farther at any given moment."
But at the White House and at the Pentagon, there is talk of better intelligence - some of it supplied by captured al-Qaida lieutenants - and a new sense of optimism.
Much of it centers on Task Force 121, which was created last fall to hunt what the military calls "high-value targets" in Iraq and Afghanistan. A senior military official in Washington with access to classified troop movements said "small numbers" of the commandos had recently moved to Afghanistan to bolster the Special Operations efforts there, a development first reported this week by The Washington Times.
The Associated Press contributed to this article.