Al Qaeda's safe haven in northwestern Pakistan is largely inaccessible to outside forces and unlikely to be eliminated by either the US or Pakistani military, top intelligence officials said.
At a hearing in the US House of Representatives, Pentagon intelligence chief James Clapper said the United States is not content to sit still while the militant network blamed for the September 11 attacks on New York and Washington regenerates its strength in North Waziristan.
"I think our objective will be to neutralise, not eliminate, but certainly make this safe haven - as we have the others - less safe and less appealing for AQ," Mr Clapper told a joint session of the House armed services and intelligence committees.
But Mr Clapper, under secretary of defence for intelligence, presented the task of eliminating al Qaeda's influence in the region as a long-term project that will hinge on US economic aid to the local populace and contributions of military assistance including sophisticated surveillance equipment to the Pakistani military.
"This is going to be a long haul process," he said. "I don't think we'll have any demonstrable change within (a) three-year time-frame."
Mr Clapper and other officials spoke to lawmakers about al Qaeda's emergence in Pakistan after White House homeland security adviser Frances Townsend refused to rule out US military action against al Qaeda in Pakistan. The Bush administration released unclassified excerpts of a major intelligence report last week that concluded the United States faces a heightened threat from al Qaeda in part because of the Pakistan safe haven.
Intelligence officials said al Qaeda ran to Waziristan after Washington and its allies drove the militants first from Taliban-ruled Afghanistan and then from urban areas inside Pakistan.
Pakistani President Pervez Musharraf has deployed more troops to Waziristan where militant tribesmen, accused of harboring al Qaeda and supporting the Taliban, have stepped up attacks after scrapping a 10-month-old peace deal with the government.
But officials appeared to play down expectations that current Pakistani military operations could include a full scale assault on al Qaeda sites in a remote mountainous region populated by hostile and heavily armed tribes.
"Al Qaeda is now in a part of Pakistan that is largely inaccessible to Pakistani forces, the Pakistani government. And it is a very difficult operating environment for them," said Edward Gistaro, the top US intelligence analyst on transnational threats.
"It is just a very difficult environment for outside forces to operate in," he added.
On Wednesday, the US Army general who heads counterterrorism operations in Afghanistan said Pakistani forces are currently engaged in "a significant military operation" that slightly decreased cross-border militant attacks in Afghanistan.