"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.

"The Justice Department and the FBI plan to ask for the public's help today in locating several suspected terrorist sympathizers, including some whose names have not been made public before

"In April, an FBI bulletin to law enforcement agencies warned of possible truck bombs. A source familiar with the government's threat discussions said yesterday that truck bombs are a primary concern. "I'm more worried than I was at Christmastime," said one senior U.S. intelligence official, comparing the "election threat" to the canceling of specific airline flights around the holidays. He said the U.S. government is convinced there are as yet unidentified al Qaeda operatives residing in the United States, waiting for the word to launch plots.

"Officials were urged to take note of people dressed in bulky jackets in warm weather, clothing smelling of chemicals or trailing electrical wires, and they warned that potential bombers may be dressed in uniform or even disguised as pregnant women.