A giant U.S.-led naval exercise began off Hawaii on Thursday with China joining its Asia-Pacific rivals for the first time, but analysts doubted the drills will ease tensions over Chinese maritime claims and some said Beijing could use them to strengthen its navy. Washington and its allies hope China's participation in the five-week Rim of the Pacific (RIMPAC) exercises, involving 55 vessels, more than 200 aircraft and some 25,000 personnel from 22 countries, will build trust and help avert misunderstandings on the high seas that could escalate into crisis. But analysts say the maneuvers may only help Beijing strengthen its growing naval capability by observing the forces of the United States and its allies. Twenty-three nations had been expected to participate in RIMPAC this year.