Federal officials have information suggesting that al Qaeda has people in the United States preparing to mount a large-scale terrorist attack this summer, sources familiar with the information said yesterday.

The concerns are driven by intelligence deemed credible that was obtained about a month ago indicating an attack may be planned between now and Labor Day.

That information dovetails with other intelligence "chatter" suggesting that al Qaeda operatives are pleased with the change in government resulting from the March 11 terrorist bombings in Spain and may want to affect elections in the United States and other countries.