Osama bin Laden nearly impossible to catch or kill, say experts - but that won't stop Osama hunters by James Gordon Meek

Killing Osama may be a top priority for President Obama, but it's almost Mission Impossible - like it was for his predecessor - if the terror leader is holed up high in Pakistan's snowy peaks, experts say.

"The new people are going to face the same problems," warned a top adviser to President Bush.

The U.S. has been secretly training for years, however, in case the CIA scores that rarest prize: Bin Laden's home address. But they already know his neighborhood.

It's been a challenge, however, gaining intel on the region. Bin Laden hunters have had to turn to Lonely Planet's now out-of-print Hindu Kush trekking guide for information. The U.S. and Indian militaries snatched up boxes of them - so many that they're now almost impossible to find.

"Who else is interested in obscure passes along the Af-Pak-Indian border?" quipped one Pakistan expert.

A close look at the Hindu Kush mountains suggests the higher Bin Laden is, particularly in winter, the harder it'll be to squash him:

Terrain: He could be anywhere in thousands of square miles of mountains among the tallest on Earth and fortified by deep, avalanche-prone snow.

Elevation: If he lives at 10-16,000 feet, U.S. hunters must be acclimatized or suffer altitude sickness, which can be fatal.

Aircraft: The huge CH-47 Chinook is the only chopper that can lift a sizeable force using oxygen to those heights, but it's a big, loud and slow target.

"With very precise information on Bin Laden's whereabouts, it would be possible to mount an operation to get him," said an ex-CIA officer in Pakistan. "The problem is getting the intel."

A "very high risk" high-altitude parachute jump or "ill-advised" chopper assault by U.S. Delta Force or Navy SEALs are both doable but arguably foolhardy, said the officer whose men last battled Bin Laden at Tora Bora in 2001 before he escaped into Pakistan.

"There is no reason to commit special ops forces" if an armed drone can simply "launch multiple Hellfire missile strikes," said former Delta Force commander and "Kill Bin Laden" author Dalton Fury - a pseudonym.

Fury devised a plan - scrapped by top brass - for his elite unit to attack Bin Laden's unguarded rear flank by traversing the Tora Bora mountains above 10,000 feet using oxygen canisters in the thinner air. But bin Laden escapedinto Pakistan.

If bin Laden lives high in the Hindu Kush, he's snowbound for winter and likely free of fear from attack.

Concern about altitude sickness - a common affliction above 9,000 feet - prompted the Army to study dozens of civilian climbers who recently scaled Tanzania's 19,340-foot Mt. Kilimanjaro to find out how to adjust soldiers to extreme heights.

"Even if you could get people acclimatized," insisted the Bush adviser, "it's hard to just drop white guys in unnoticed."

Experts point to the disaster of 19 troops killed in a secret mission in 2005 as a learning lesson.

Three SEALs died in a firefight after tribal goatherds spotted them, and 16 more troops perished in a botched Chinook rescue in the Chitral region.

The huge, lumbering twin-rotor chopper can haul troops up to 16,000 feet, but it is "not very stealthy," said a retired aviator.