KABUL: Osama bin Laden's days may well be numbered, as increasingly confident statements by the US military in Kabul are matched by heightened activity along the Afghan-Pakistan frontier.

But experts on the Al Qaeda network and the ousted Taliban warn that catching the world's most wanted man will not be easy, especially if they want him alive.

"A focus of political will and resources will clearly increase the chances of high quality targets being hit," said Jason Burke, a leading expert and author on Al Qaeda. "The problem is that the practical difficulties operating there remain, as do the obstacles posed by massive local support for the fugitives."

US officials no longer question whether the Saudi-born dissident accused of masterminding the September 11, 2001 attacks is alive, even though the most recent definite proof is nearly two years old.

Visiting Kabul on Thursday, US Defence Secretary Donald Rumsfeld said he believes Osama will be caught, but has no idea when. His soldiers have been less coy.

Lieutenant-Colonel Matt Beevers, the US military spokesman in Afghanistan, spoke this week of "renewed urgency" in hunting down key terror figures, including Osama.

"We feel that really the sands in this guy's hour glass...are running out. We remain committed and reaffirmed in our effort to track these guys down and get them." If the US or Pakistani military know where Osama is, even roughly, they are not saying so.

Officers on both sides of the Afghan-Pakistan border where Osama and his right-hand man Ayman al-Zawahri are widely thought to be hiding scoffed at a recent report locating him in a 10-sq-mile area north of Quetta.

Analysts doubt the existence of specific intelligence pinpointing the whereabouts of Osama. The 2,450-km Afghan-Pakistan border is an ideal place to hide, running through sparsely populated mountains and deserts, where many local Pushtun tribesmen are sympathetic to Osama and fiercely protective of fugitives.

Pakistan has beefed up its military presence in the semi-autonomous Federally Administered Tribal Areas (Fata) along the frontier and the 10,600-strong US-led force in Afghanistan has promised a major spring offensive to hunt militants.

They hope to create a "hammer and anvil" effect to stop militants including Osama, al-Zawahri and Taliban supreme commander Mullah Mohammad Omar from slipping across the porous and ill-defined border seemingly at will.

There is a new sense of urgency in Islamabad to cooperate with US forces that was not there before, analysts say.

Some tie it to two assassination bids on Pakistani President Pervez Musharraf late last year that he says may be linked to Al Qaeda, and a nuclear proliferation scandal that has Pakistan scrambling to repair the damage to ties with Washington.

For America's part, Osama's head on a platter would be a huge boost for President George W. Bush in election year. -Reuters