SINGAPORE—Tensions between the U.S. and Chinese militaries continue to simmer even as their leaders prepare for a likely summit in the coming weeks, a sign of the difficulties the two global powers face in managing one of the most sensitive aspects of their relationship.

The discord occupied center stage this week at a security conference in Beijing, where a top Chinese general took veiled swipes at Washington’s foreign policy and military posture, characterizing them as grave threats to peace and stability around the world as wars rage in Ukraine and Gaza.