WASHINGTON — Al Qaeda is stepping up its efforts to sneak terror operatives into America and has acquired most of the capabilities it needs to strike here, according to a new American intelligence assessment.

The draft National Intelligence Estimate is expected to paint an ever-more-worrisome portrait of Al Qaeda’s ability to use its base along the Pakistan-Afghan border to launch and inspire attacks against America over the next several years.

Yet, the government’s top analysts concluded that American soil has become a harder target for the extremist network, thanks to worldwide counterterror efforts since the attacks of September 11, 2001.

Among the key findings of the classified estimate, which is still in draft form and must be approved by all 16 American spy agencies:

– America will face “a persistent and evolving terrorist threat” within its borders over the next three years. The main danger comes from Islamic terrorist groups, especially Al Qaeda, and is “driven by the undiminished intent to attack the homeland and a continued effort by terrorist groups to adapt and improve their capabilities.”

– Al Qaeda is probably still pursuing chemical, biological or nuclear weapons and would use them if its operatives developed sufficient capability.

– The terror group has been able to restore three of the four key tools it would need to launch an attack on American soil: a safe haven in Pakistan’s tribal areas, operational lieutenants and senior leaders. It could not immediately be learned what the missing fourth element is.

– The group will bolster its efforts to position operatives inside American borders. In public statements, American officials have expressed concern about the ease with which people can enter America through Europe because of a program that allows most Europeans to enter without visas.

The document also discusses increasing concern about individuals already inside America who are adopting an extremist brand of Islam.

On a positive note, analysts concluded that increased international efforts over the past five years “have constrained the ability of Al Qaeda to attack the U.S. homeland again and have led terrorist groups to perceive the homeland as a harder target to strike than on 9/11.”

Those measures helped disrupt known plots against America, the analysts found.

National Intelligence Estimates are the most authoritative written judgments that reflect the consensus long-term thinking of senior intelligence analysts.

Government officials, who spoke on condition of anonymity because the report has not been finalized, described it as an expansive look at potential threats within America and said it required the cooperation of a number of national security agencies, including the CIA, FBI, Homeland Security Department and National Counterterrorism Center.

National security officials met at the White House on Thursday about the intelligence estimate and related counterterrorism issues. The tentative plan is to release a declassified version of the report and brief Congress on Tuesday, one government official said.

A spokesman for National Intelligence Director Mike McConnell, Ross Feinstein, declined to discuss the document’s specific contents. But he said it would be consistent with statements made by senior government officials at congressional hearings and elsewhere.

The estimate echoes the findings of another analysis prepared by the National Counterterrorism Center earlier this year and disclosed publicly on Wednesday. That report — titled “Al Qaeda better positioned to strike the West” — found the terrorist group is “considerably operationally stronger than a year ago” and has “regrouped to an extent not seen since 2001,” a counterterrorism official familiar with the reports findings told the AP.

On Thursday, news of the counterterrorism center’s threat assessment renewed the political debate about the nature of the Al Qaeda threat and whether American actions — in Iraq in particular — have made America safer from terrorism.

At a news conference Thursday, President Bush acknowledged Al Qaeda’s continuing threat to America and used the new report as evidence his administration’s policies are on the right course.

“The same folks that are bombing innocent people in Iraq were the ones who attacked us in America on September 11,” he said. “That’s why what happens in Iraq matters to security here at home.”

Yet Senate Intelligence Committee Chairman Jay Rockefeller, Democrat of West Virginia, said Iraq has distracted America. He said America should have finished off Al Qaeda in 2002 and 2003 along the Afghan-Pakistan border.

Instead, “President Bush chose to invade Iraq, thereby diverting our military and intelligence resources away from the real war on terrorism,” Mr. Rockefeller said. “Threats to the United States homeland are not emanating from Iraq. They are coming from Al Qaeda leadership.”

Mr. Rockefeller, who voted in favor of toppling Saddam Hussein, called for America to end its involvement in what he called the Iraqi civil war.

In recent weeks, senior national security officials have been increasingly worried about an Al Qaeda attack in America.

Appearing on a half-dozen morning TV shows Thursday, Homeland Security Secretary Michael Chertoff laid out a list of factors contributing to his “gut feeling” that the nation faces a higher risk of attack this summer: Al Qaeda’s increased freedom to train in South Asia, a flurry of public statements from the network’s leadership, a history of summertime attacks, a broader range of attacks in North Africa and Europe, and homegrown terrorism increasing in Europe.

“Europe could become a platform for an attack against this country,” Mr. Chertoff told CNN, although he and others continue to say they know of no specific, credible information pointing to an attack here.

National security officials are frustrated by an agreement last year between President Musharraf of Pakistan and tribal leaders in western Pakistan, which gave tribes near the Afghan border greater autonomy and has led to increased Al Qaeda activity in the region.

Nevertheless, Bush administration officials still view Mr. Musharraf as a partner.

Speaking to a congressional hearing, Assistant Secretary of State Richard Boucher said that Pakistan under Mr. Musharraf has captured more Al Qaeda operatives than any other country and that several major Taliban leaders were captured or killed this year.

“There is a considerable Al Qaeda presence at the border, but they are under pressure,” Mr. Boucher told a House national security subcommittee.

Rep. Jim Cooper, Democrat of Tennessee, was skeptical, saying Al Qaeda leader Osama bin Laden and other terrorist leaders apparently feel safe there. “Is this a Motel 6 for terrorists?” he asked.