Bin Laden's hideout in wilds of Pakistan

The dirt road that connects Pakistan's remote town of Wana with Afghanistan is lined with walled compounds. They form the outermost ramparts for Osama bin Laden's hideaway of forests, mountains, and ravines, local residents and officials say.

The compounds are believed to be part of the concentric circles of defense that insulate senior Al Qaeda leaders, giving them plenty of early warning in the event of a ground assault here.

Although US officials say they have set their sights on a 20-square-mile section within this northwestern region of South Waziristan, they face a number of obstacles to going after America's Enemy No. 1.

The terrain here is as treacherous politically as geographically. Government control is tenuous in this fiercely conservative district of Pakistan's tribal belt, where tribesmen share the Taliban's Pashtun ethnicity.

Local residents and officials recently gave a reporter a tour of the zone near Wana, the district capital, which they described as "infested" with Al Qaeda members.

Authorities in Wana say eight people have been gunned down in the tiny hamlet of Angoor-ada on suspicion of being US informants, leaving local residents terrified to cooperate. They believe the heavily armed tribesmen hosting the Al Qaeda leadership are too loyal, too well-paid, or too terrified to give information on the Saudi fugitive they are believed to be hiding.

A video of bin Laden and his deputy, Ayman al-Zawahiri, aired by the Arab TV network Al Jazeera on the eve of the 9/11 anniversary unfolded in a mountainous landscape. It showed the two men picking their way down a rocky slope, past thick pine and cedar trees, dressed in the style of Pashtun tribesmen. It was not clear, however, when the video was filmed, though an audio track released with the silent video refers to recent terror attacks in Iraq.

US officials say they have narrowed the zone of interest to an area slightly larger than the field of battle on the nearby Tora Bora mountain range, where US and Afghan forces launched an attempt to capture bin Laden in December 2001.

This time around, officials acknowledge that a complex set of sensitivities - and the simple fact that America's military has been busy in Iraq - have stymied hopes of an aggressive campaign in the area.

Particularly sensitive is the issue of US forces operating missions inside Pakistan, a country where antiAmerican sentiment runs high and where many take a dim view of the US military presence in Afghanistan and Iraq. US officials say they fear a joint military operation in the semi-autonomous tribal belt could result in grave consequences for President Pervez Musharraf, who has survived at least three assassination attempts since he threw his support behind the US-led war on terror in September 2001. A coalition of conservative Islamic political parties is already pushing for Musharraf's ouster, and would probably win wider public support if US troops entered Pakistan, analysts say. "If we lose Musharraf, all bets are off for Pakistan," says a senior American official who has worked extensively on the region.

US Special Forces do patrol just over the Afghan border from South Waziristan out of a base in Shkin in Paktika Province. But some US officials in the region complain that many units, especially those with Arab-language skills, were shifted to Iraq.Though US soldiers are officially banned from crossing the border, some recent engagements have dipped into Pakistan, including one that left two Pakistani soldiers dead - an event that strained an already delicate situation.

Pakistan maintains a brigade of soldiers in the Ziar-e-Noor base just outside Wana, and there have been some small operations to root out terror suspects in South Waziristan. But military officials here say their troops are stretched too thin across the extensive Pakistani-Afghan border - too poorly funded and equipped to launch a major operation on their own. In recent weeks, hundreds more soldiers and military hardware have been moved into nearby bases in the tribal belt, though officials here insist it was a routine rotation, and denied local press reports that US troops were slipped in with them.

One factor for US intelligence is trust in their Pakistani counterparts, Pakistan's Inter-Services Intelligence (ISI). US authorities give credit to hard work by the ISI, which has been instrumental in the capture of leading Al Qaeda operatives like Khalid Sheik Mohammed, the alleged mastermind of the 9/11 attacks. But while they praise the overall level of cooperation, they worry that some ISI officials remain loyal to the extremist groups they have supported for decades in the proxy war over Kashmir with arch rival India. "It will be difficult for the ISI to completely dismantle these groups," says Pakistani journalist Rahimullah Yusufzai, "since they may one day be necessary again in Kashmir."

Gaining local intelligence support is a crucial issue for the US, say American officials, since the spy satellites and predator drones scanning the tribal belt have gleaned little useful intelligence in recent months. "We are fighting a high-tech war against a low-tech enemy," says a US official. "We're looking for the funds in Swiss bank accounts when the money is in the coffee can. We're tapping telephones when they are passing notes by donkey."

Pakistani intelligence officials agree that camels and donkeys are often the conduit for illicit messages passed between terror chieftains. Meanwhile, Afghan commanders fighting a resurgent Taliban army north of the border report having pulled letters written by Taliban commanders from bodies of dead enemy soldiers. Many now believe there is an extensive network of handwritten messages extending across southern Afghanistan.

Moving people is similarly low tech. Officials on both sides of the border say an extensive network of local "guides" - Afghans or Pakistanis loyal to Al Qaeda and the Taliban - shuttle top officials through populated areas where they run the highest risk of getting caught. They do the shopping, buy food, pay off local police guards - anything necessary to keep their cargo hidden and off the streets.

Pakistani officials in Waziristan and some US officials discount the notion that bin Laden himself moves very far very often, saying it is more likely the terror boss is confined within a small area.

Despite the obstacles to launching a push for Al Qaeda operatives in Pakistan's tribal belt, many here fear the cost could grow higher if the situation is allowed the fester. Afghan officials have charged that resurgent Taliban are regrouping in Pakistan's border regions and organizing killings inside Afghanistan that threaten to destabilize the government of President Hamid Karzai.

"Why did we start this war at all if we are going to back down now?" asks Ayub Palawan, a garrulous Afghan commander who battles Taliban forces almost weekly from his base in southern Spin Boldak. "Osama looks stronger with every day he eludes the Americans."

• A local reporter traveled to South Waziristan and contributed to this report.