BANGKOK Some 10,000 troops fanned out across northern Thailand Tuesday as annual U.S., Thai and Singaporean war games got underway with a focus on peacekeeping and law enforcement, AFP said. Codenamed "Cobra Gold," the exercise attracted observers from nine nations and is one of the biggest annual training events involving U.S. forces in the Asia Pacific region. U.S. officials said China and Vietnam had been invited to send an observer each but had declined to do so.