They also met with China’s defense minister, its vice premier for economic policy, its foreign minister and the head of its rubber-stamp legislature. Mr. Trump has said on social media that he would likely visit China early next year. Still, many areas of disagreement remain — including over China’s military presence in the Pacific, which has grown more assertive. The U.S. military has accused Chinese planes of flying dangerously close to American planes, nearly causing collisions. China has countered that American aggression is fueling the risks.