Senators Warned of Terrorist Attack on U.S. by July

America’s top intelligence official told lawmakers on Tuesday that Al Qaeda and its affiliates had made it a high priority to attempt a large-scale attack on American soil within the next six months.

The assessment by Dennis C. Blair, the director of national intelligence, was much starker than his view last year, when he emphasized the considerable progress in the campaign to debilitate Al Qaeda and said that the global economic meltdown, rather than the prospect of a major terrorist attack, was the “primary near-term security concern of the United States.”

At Tuesday’s hearing, Senator Dianne Feinstein, Democrat of California and chairwoman of the Senate Intelligence Committee, asked Mr. Blair to assess the possibility of an attempted attack in the United States in the next three to six months.

He replied, “The priority is certain, I would say” — a response that was reaffirmed by the top officials of the C.I.A. and the F.B.I.

Citing a recent wave of terrorist plots, including the failed Dec. 25 attempt to blow up an airliner as it approached Detroit, Mr. Blair and other intelligence officials told a Senate panel that Al Qaeda had adjusted its tactics to more effectively strike American targets domestically and abroad.

“The biggest threat is not so much that we face an attack like 9/11,” said Leon E. Panetta, the C.I.A. director. “It is that Al Qaeda is adapting its methods in ways that oftentimes make it difficult to detect.”

As the C.I.A. continues its drone attacks aimed at Qaeda operatives in Pakistan, the officials also said that the network’s splinter groups in Yemen and Somalia were taking on more importance.

But Mr. Blair began his annual threat testimony before Congress by saying that the threat of a crippling attack on telecommunications and other computer networks was growing, as an increasingly sophisticated group of enemies had “severely threatened” the sometimes fragile systems undergirding the country’s information infrastructure.

“Malicious cyberactivity is occurring on an unprecedented scale with extraordinary sophistication,” he told the committee.

His emphasis on the threat points up the growing concerns among American intelligence officials about the potentially devastating results of a coordinated attack on the nation’s technology apparatus, sometimes called a “cyber-Pearl Harbor.”

He said that the surge in cyberattacks, including the penetration of Google’s servers from inside China, was a “wake-up call” for those who dismissed the threat of computer warfare. “Sensitive information is stolen daily from both government and private-sector networks, undermining confidence in our information systems, and in the very information these systems were intended to convey,” Mr. Blair said.

In another departure from last year’s testimony, Mr. Blair appeared alongside other top intelligence officials, including the heads of the C.I.A., the F.B.I. and the Defense Intelligence Agency. Last year, the intelligence director sat alone before the committee, a partly symbolic gesture intended to demonstrate the authority of the director, whose office has been criticized for commanding little power over America’s 16 intelligence agencies.

At times, the senators seemed more interested in debating one another than in hearing testimony from witnesses. Midway through the hearing, partisan bickering broke out about whether terrorist suspects ought to be tried in civilian courts and whether the man charged as the Dec. 25 bomber should have been given Miranda rights that could protect him against self-incrimination.

As senators traded barbs, the intelligence officials stared stonily ahead or shuffled their notes.

The intelligence chiefs also raised warnings about nuclear proliferation, particularly focusing on Iran and North Korea.

Mr. Blair said that Iran “has the scientific, technical and industrial capacity to eventually produce nuclear weapons,” and that the discovery of a secret enrichment plant near Qum heightened suspicions about Iran’s intentions to build a nuclear bomb.

Still, he said that Tehran was following a “cost-benefit approach” to its nuclear decision-making and that it remained unclear whether Iran’s leadership would make a political calculation to begin producing weapons-grade uranium, allowing other nations to “influence” that decision through diplomatic steps.