SINGAPORE—Vice President Mike Pence hit out at China during his tour through Asia, signaling an increasingly tough line against Beijing as the world’s two largest economies clash over trade, security and human rights.

In a speech Thursday at a summit of Asian nations, Mr. Pence warned that “empire and aggression have no place in the Indo-Pacific.” He didn’t mention any country by name, but White House aides left little doubt the reference was to China. The U.S., Mr. Pence said, “seeks collaboration, not control.”

Mr. Pence, who is emerging as the Trump administration’s most hawkish voice on China, is spending nearly a week in Asia at summits and assuring smaller nations that the U.S. remains a reliable bulwark against China’s military moves and economic influence.

The meetings in Singapore, held under the umbrella of the Association of Southeast Asian Nations, reflect competing visions by the U.S. and China, which smaller countries increasingly fear will force them to choose between major powers key to their trade and security.

A senior administration official said at a media briefing that Mr. Pence will detail the administration’s strategy at his next stop, in Papua New Guinea for the Asia-Pacific Economic Cooperation forum.