LONDON Muammar Gaddafi's pursuers must act fast to stop the trail going cold or risk prolonging Libya's war by months, if not years, analysts say.
Hunting anyone in a sparsely-populated desert country three times the size of France is a daunting task, let alone a well-connected former head of state with access to gold and guns.
Material resources are not the only factors favoring the fugitive Colonel.
Die-hard fighters remain active in several regions, his companions probably include an inner circle of still-feared security men, and he can rely on friends among southern Libyan tribes and nomadic communities of smugglers in the Sahel.
Much of the interior, especially the south-west, remains outside rebel control and includes places where locals are either undecided about the revolution or openly hostile to it.
Time is pressing, for the longer his vanishing act goes on, the more an aura of invincibility could grow around him.
"The best time to capture these defeated leaders is immediately after the conflict finishes," former U.N. chief in Bosnia Paddy Ashdown told Reuters.
"The longer it takes the more chance they have of being spirited away to a place which is much more difficult to find, as we saw with Saddam Hussein, Osama Bin Laden, (Radovan) Karadzic and (Ratko) Mladic."
In Tripoli, a group of rebels stepped up efforts to track him down on Thursday, besieging a cluster of apartment buildings where they believed he was holed up. Outside the capital, rebel forces harried Gaddafi loyalists along the coastal road.
FALSE INDENTITIES, DISGUISES
Finding Gaddafi may not take as long as the 13 years it took authorities to grab Bosnian war crimes suspect Karadzic, or the decade it took the United States to find and kill bin Laden after the attacks of Sept 11, 2001.
Bosnian war crimes suspects used military contacts, false identities and occasionally disguises to evade detection. Bin Laden hid in plain sight near the Pakistani army's main academy in a northwestern garrison town.
Whether Gaddafi has the scope or ingenuity to adopt any of those tactics is not clear, but rebels won't want to give him the time to develop expertise.
"Now is the crucial moment," added Ashdown, a former British special forces officer.
"Once they have managed to reinsert themselves back into a secure place away from the battlefield and are living amongst the population who regard them as heroes, this is a difficult and long term proposition."
Gaddafi's experience of undermining international sanctions in the 1980s and 1990s will stand him in good stead, for in that period he cultivated smuggling networks and overseas financiers who helped move money and weapons around the world.
And his ability to evade detection may draw support from safe houses and arms stashes that his security men are presumed to have prepared for an emergency such as this.
Graham Cundy, a British military specialist at Diligence, a security and intelligence consultancy, said he expected Gaddafi would use tactics similar to those employed, initially successfully, by Iraqi insurgent Abu Musab al-Zarqawi and Taliban military chief Mullah Dadullah Lang, before they were eventually tracked down and killed.
He lists the essential tasks as:
-- Avoid using mobile phones, or phones at all, directly.
-- Use trusted gate keepers to relay your messages.
-- Avoid overt signs of protection - armored or large convoys, large bodyguard details that can be seen by drones.
-- Consider the use of doubles and misdirection.
Money helps to buy loyalty, weapons and silence.
Gaddafi's former central bank governor Farhat Bengdara was reported as saying he would try to sell part of Libya's gold reserves to pay for his protection and sow chaos among tribes.
GADDAFI HEADS TO THE DESERT?
Bengdara, who has allied himself with the rebels, told the Italian daily, Corriere della Sera, that an ally of Gaddafi had offered 25 tonnes of gold to his friend "a little time ago."
Tribes, and the lands they control, will also be important.
Noman Benotman, a former Islamist guerrilla commander now with Britain's Quilliam think-tank, told Reuters he suspected Gaddafi had retreated to a military compound at al-Jufra south of his hometown of Sirte.
Al-Jufra had been well prepared as the military's main national command center under army chief Abu Bakr Younus Jabr and has a significant defenses, he said, noting it lay strategically on the main route between Sirte and Sebha.
An influential tribe in Sebha is the Megarha, whose loyalty remains unclear. Analysts say an August 21 public denunciation of Gaddafi by his former number two, Abdel Salam Jalloud, a Megarha, might help ensure the tribe sided with the rebels.
Gaddafi appeared to suffer another blow to his tribal support on Aug 24 when Cairo-based cousin and longtime close associate, Ahmed Gaddaf al-Dam, a member of Gaddafi's Gaddafa tribe, backed a rebel call to avoid more bloodshed.
There is little firm information about the whereabouts of other key figures in Gaddafi's inner circle. Many are believed to be still at large in Libya or neighboring countries.
These include Ahmed Ibrahim, an outspoken Gaddafi hard-liner who is a cousin of Gaddafi and a member of his Gaddadfa tribe, Abdullah Sanussi, Gaddafi's brother-in-law and internal security chief and Abdulkader Youssef Dibri, head of Gaddafi's personal security and responsible for managing Libyan official assets. Some suspect Dibri is in Egypt.
GADDAFI'S TOP SMUGGLER "ARRESTED"
Other figures include Bashir Saleh, Gaddafi's chief of staff and a reputed expert on smuggling and sanctions-busting. Saleh was reported by Al-Arabiya television on Thursday to have been captured with his children at a family farm in Tripoli. There was no immediate confirmation of the report.
There has been no word of the whereabouts of Gaddafi's foreign spy chief Bouzaid Dordah. A former prime minister, Dordah has a reputation of being one of the few people confident enough to speak his mind bluntly in front of Gaddafi.
NATO is expected to provide a large amount of intelligence help to the manhunt, in the form of electronic eavesdropping. Special forces teams, either working for private contractors or for member states' armies, are probably involved.
But the hunt's most important asset could be the prevailing political climate, because information about Gaddafi's location would be easier to obtain if his close aides prepared to defect.
To that end, argues Saad Djebbar, a former adviser to the Libyan government, the rebels should show they are serious about including a wide cross section of Libyan politics and society in a new transitional government.
Rapid aid flows to newly liberated zones would help show Libyans that the revolution has brought benefits, he said.
(Reporting by William Maclean)