WASHINGTON (CNN) -- Al Qaeda is the strongest it has been since the aftermath of the September 11, 2001, terrorist attacks, a new U.S. government analysis concludes, according to a senior government official who has seen it.

A Pakistani soldier mans a bunker near the Afghan border in a tribal area of Pakistan.

Despite a campaign of military action and counterterrorism operations, al Qaeda has regained its strength and found safe haven in the tribal areas of Pakistan, the report says, according to counterterrorism officials familiar with the report.

The five-page intelligence analysis remains classified and was prepared for senior U.S. policymakers. It was not issued in response to a specific threat.

Two intelligence officials said the report's finding are similar to what is expected to be in the National Intelligence Estimate anticipated to be released later this summer. The NIE is the intelligence community's collective analysis of pressing national security issues.

The White House's view is that "over the past six years, we have prevented attacks from al Qaeda by taking the fight to them," a senior administration official said. "But they are an enemy that adapts."

This new report backs up warnings by Homeland Security Secretary Michael Chertoff and other officials that al Qaeda remains a serious threat and that the United States is vulnerable despite the numerous security changes made since September 11, 2001. Watch Chertoff explain his "gut feeling" »

Chertoff said Wednesday, however, that there is no "specific, credible information" that terrorist attacks on the United States are imminent.

In a House Armed Services Committee hearing Wednesday, several senior intelligence officials talked about how the terrorist group has found refuge in parts of Pakistan.

"We actually see the al Qaeda central being resurgent in their role in planning operations," John Kringen, head of the CIA's intelligence directorate, testified at the hearing Wednesday. "They seem to be fairly well settled into the safe haven in the ungoverned spaces of Pakistan there. We see more training. We see more money. We see more communications."

Thomas Fingar, deputy director of national intelligence, told lawmakers that al Qaeda leaders hiding in Pakistan are able to maintain relationships "with affiliates throughout the Middle East, North and East Africa and Europe."

In a statement, Senate Majority Leader Harry Reid said it was no surprise al Qaeda has been able to reorganize and rebuild "given President Bush's stubborn dedication to keeping our overextended military mired in an Iraqi civil war."

"It is a travesty that Osama bin Laden remains at large nearly six years after the 9/11 attacks and appears to have found new sanctuary to operate freely in the Afghanistan-Pakistan border regions," Reid said. "The Bush administration and most congressional Republicans would rather stubbornly stick with a flawed strategy and fight a war that senior military leaders say cannot be won militarily, than adapt to fighting the enemy who attacked us six years ago."

In recent weeks, counterterrorism authorities have expressed concern about the possibility of another attack on U.S. soil, saying several factors, such as the thwarted terror plots in Britain, have them on edge.

The FBI has created a small group of agents and analysts to examine new threats and leads over the summer, a bureau official told CNN. The group, which was created several weeks ago, is supplementing what agents and others are also doing in field offices across the country and is an example of how the government is trying to make sure no credible lead is missed, the official said. E-mail to a friend

CNN's Carol Cratty, Kevin Bohn and Pam Benson contributed to this report.

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