Defense Secretary Ash Carter says the U.S. will sharpen what he calls its "military edge" to remain a key power in the Asia-Pacific region.

Carter made the pledge Thursday in a speech in San Diego. The remarks are meant to set the stage for a meeting Friday in Hawaii with his counterparts from 10 Asian nations.

The Pentagon chief describes what he calls the next phase of a U.S. pivot to Asia — a rebalancing of security commitments after years of heavy focus on the Middle East.

He said the Pentagon will make its attack submarines more lethal and spend more to build undersea drones that can operate in shallower waters where submarines cannot.