Attorney General John Ashcroft’s warning that terrorists may strike the USA this summer was based on a stream of intelligence that indicated that al-Qaeda is emboldened by its successful attacks in Madrid and deadly assaults in Iraq, three senior federal law enforcement officials who have reviewed the threat material said Thursday. The content of the threat information behind Wednesday’s warning has not changed substantially since the railway bombings in Spain in March, and it has not yielded any plots against the USA, the officials said. But terrorism analysts have detected that al-Qaeda’s ranks, while depleted since the Sept. 11 attacks, have been re-energized by the recent strikes, the officials said. As a result, there is fear that a string of high-profile events throughout the summer, including the national political conventions in Boston and New York, could pose irresistible targets to terrorists. Full Story