U.S. intelligence officials say they're severely limited and deeply frustrated by their efforts to track down Usama bin Laden (search) along the lawless border between Pakistan and Afghanistan.

The New York Times first reported that CIA agents, in their efforts to locate the Al Qaeda leaders, established covert bases in the mountains of northwest Pakistan in late 2003. The newspaper reported that those bases have been largely ineffective because of strict limits placed on them by officials in that country. For example, the agents were not free to move around the country and had to be escorted by Pakistani officials.

The Times also reported that bin Laden is in charge of an elite cell of Al Qaeda terrorists who are still planning to attack the United States.

On Monday, a spokesman for the U.S. military in Afghanistan said he couldn't comment on CIA operations. He said American forces were relentlessly searching for clues to bin Laden's whereabouts.

"No matter where he is, whether he is in Afghanistan, whether he is in Pakistan or wherever he is, I think we share [Afghan] President [Hamid] Karzai's sentiment that some day ... he will be brought to justice," Maj. Mark McCann told a press briefing in Kabul.

A spokeswoman at the U.S. Embassy in Kabul also said she couldn't speak for the CIA.

Pakistan said Monday there was no evidence bin Laden is hiding in the country, and denied it allowed CIA agents to set up bases along the border to search for him.

Pakistani and American generals agree the trail for bin Laden has gone cold, more than three years after the Sept. 11, 2001, attacks.

Pakistani Foreign Ministry spokesman Masood Khan said bin Laden had not been seen anywhere, and scoffed at reports he might be hiding in Chitral, in the country's scenic north.

"Usama bin Laden has not been sighted in Chitral or in any other part of Pakistan," Khan said, adding, "there are no operations being conducted by U.S. forces inside Pakistan."

President Gen. Pervez Musharraf (search) has previously acknowledged that a small number of American experts were working with Pakistani troops in operations against Al Qaeda militants. But he has denied that U.S. forces — deployed in neighboring Afghanistan — are actively hunting bin Laden in Pakistan.

White House spokesman Scott McClellan on Monday was asked about whether any progress was being made in the hunt.

"He will be brought to justice," the spokesman told reporters. "I think we've made it very clear that we are continuing to pursue Al Qaeda leaders who are responsible for the attacks on innocent Americans who lost their lives on Sept. 11, 2001. We are making great progress in dismantling the Al Qaeda network. There is more to do."

Bin Laden is believed to be hiding in the tribal regions along the Pakistan-Afghanistan border, a rugged region where tribal leaders are believed to be protecting him. Pakistan's army has mounted a series of bloody offensives against foreign fighters near the border this year, and American forces launched a winter-long operation last week against Taliban rebels on the Afghan side.

The issue of the still-at-large bin Laden is a sensitive one for Musharraf, who is under pressure at home from hard-liners opposed to his strong ties with Washington.

"There are no CIA cells in Pakistan ... in our tribal areas, and there is absolutely no truth in this New York Times report," said army spokesman Maj. Gen. Shaukat Sultan.

A senior Pakistani counterterrorism official said Monday U.S. officials had not found intelligence on bin Laden's whereabouts, although their information had helped nab some Al Qaeda suspects in Pakistan.

"Whenever U.S. intelligence and communication experts come up with some specific information, and they need our help, we organize things, act on their tips, but the operations are conducted by our own security forces," he said.

Karzai said Sunday that bin Laden is "definitely" in the region and eventually will be caught, even though American and Pakistani generals admit the trail is cold.

"It's very difficult to say where he is hiding. He cannot be away from this region. He's definitely in this region," Karzai said on a television news show. "We will get him sooner or later, trust me on that."

According to the Times, U.S. officials now believe bin Laden's No. 2 man, Ayman al-Zawahiri (search), is also in the region but that he has been separated from bin Laden for security reasons. The paper also reports that U.S. military and intelligence personnel in Afghanistan are no longer actively searching for the terror ringleader.

President Bush met with Musharraf on Dec. 4 at the White House. During a joint press appearance, Bush said the two leaders "are absolutely committed to fighting off the terrorists who would destroy life in Pakistan, or the United States, or anywhere else."

Reporters then asked Bush whether he was disappointed that the Pakistani army appears to have "downgraded" their search for and hasn't yet found the Sept. 11 mastermind.

"Quite the contrary," Bush responded. "His army has been incredibly active and very brave in southern Waziristan flushing out an enemy that had thought they had found safe haven. His army has suffered casualties and for that we want to thank their loved ones for the sacrifice that their family has made. The president has been a determined leader to bring to justice not only people like Usama bin Laden, but to bring to justice those who would inflict harm and pain on his own people.

"And I am very pleased with his efforts and his focused efforts. In our discussions today, we determined how best we can help the president achieve his objective, which is not only protecting himself, but to protect his country," Bush continued.

Musharraf told FOX News' Rita Cosby in an exclusive interview earlier this month that the withdrawal of Pakistani army troops from the region near the Afghanistan border where bin Laden was believed to be was merely "a readjustment of position, a tactical readjustment."

Musharraf also said a bigger standing Afghan army is the key to quashing terror in Afghanistan, not more U.S. forces in the hunt for bin Laden.

"I would think that it may be better that we go faster on raising up an Afghan national army," he said, "increase their strength."

Musharraf also would not rule out that bin Laden could be in Iran, and not in the tribal region on Pakistan's western border.

"The possibility exists," he said. "Because people do manage to move unnoticed. These are mountainous, inaccessible areas, where movement is not all that difficult or impossible."

FOX News' Steve Centanni and The Associated Press contributed to this report.