WASHINGTON - The suicide bombers who struck Baghdad this week used thousands of pounds of plastic explosives and diversionary tactics that are hallmarks of al-Qaida, a senior U.S. counterterrorism official said Thursday. The way the attacks were carried out has made American investigators believe they could be seeing a change in tactics by those attempting to drive U.S. forces out of Iraq, the official told The Associated Press in an interview. "We're looking at that as the start of something that may be forewarning of future events," said the official, who spoke on condition of anonymity. The New York Times...