WASHINGTON  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.