The top US military officer begins a four-day trip to China on Sunday in another sign of warming military ties between the two countries after a break in relations following a $6.3 billion US arms deal with Taiwan. Admiral Mike Mullen, chairman of the US Joint Chiefs of Staff, was leaving Washington on Friday afternoon for a visit to Beijing at the invitation of his counterpart, General Chen Bingde, chief of the general staff of the People’s Liberation Army, who visited Washington earlier this year. “Admiral Mullen looks forward to continuing the engagement and dialogue that began during General Chen Bingde’s visit to the United States in May,” said Pentagon spokesman Colonel David Lapan.