* U.S. "delighted" China will participate
* China's involvement to be limited, adhere to U.S. law
* China sent observers in 1998
China's People's Liberation Army has accepted an invitation to participate for the first time in a major U.S.-hosted naval drill, but legal restrictions will limit its role to less sensitive exercises, like disaster relief, U.S. officials say.
Beijing's agreement to join the drills being held next year comes at a moment of heightened tensions between China and U.S. ally Japan over disputed East China Sea islets, and unease in the United States about China's rapid military buildup and its cyber capabilities.
The Rim of the Pacific exercise, known as RIMPAC, is billed as the world's largest international maritime exercise, with 22 nations and more than 40 ships and submarines participating the last time it was held off Hawaii in 2012.
Not all the participants are treaty allies with the United States. Last year's participants included Russia and India.
But China has never participated in the event, although it did send observers to RIMPAC in 1998, the Pentagon said.
Deputy Defense Secretary Ashton Carter acknowledged China had agreed to participate in RIMPAC during a little-noticed speech on Wednesday in Jakarta. Carter said he was "delighted that they have accepted" the American invitation, extended last year by then-Defense Secretary Leon Panetta.
At the time, Panetta said he asked China to send a ship to the exercises. Beijing said later it would give the offer "positive consideration."
"We seek to strengthen and grow our military-to-military relationship with China, which matches and follows our growing political and economic relationship," Carter said, according to prepared remarks on the Defense Department's website.
U.S. law prohibits the Pentagon from any military contacts with the PLA if it could "create a national security risk due to an inappropriate exposure" to activities including joint combat operations.
There is an exemption for operations or exercises related to search and rescue and humanitarian relief, and China participated with the United States last year in a counter-piracy drill.
Lieutenant Colonel Catherine Wilkinson, a Pentagon spokeswoman, said China's participation in RIMPAC would adhere to U.S. law and noted precautions taken by the Navy in drills to avoid revealing sensitive information.
"The U.S. Navy has operational security safeguards to protect U.S. technology and tactics, techniques and procedures from disclosure," Wilkinson said.
Dean Cheng, an analyst at the Heritage Foundation, a conservative Washington think tank, questioned whether Chinese intelligence operatives would not benefit from their participation in RIMPAC, which also includes live-fire exercises by key U.S. allies.
"If they have a frigate, or even a hospital ship, in the middle of that exercise, the hospital ship is going to be staffed by intelligence officers," Cheng said.
He noted that if the drills were designed in a way that was unhelpful to the Chinese, they would also be unhelpful to allies.
Wilkinson declined to speculate about which drills China might participate in, noting the agenda had not yet been set for next year's event.
"U.S.-China military-to-military engagements can include a range of activities in areas of mutual interest including maritime security, military medicine and humanitarian assistance/disaster relief," she said.
Commander Charles Brown, a spokesman for the Navy's Third Fleet, said the initial planning conference for RIMPAC 2014 would take place in May.
"We're proud of our ability to design an exercise that everyone feels meets their objectives and is comfortable with," Brown said.