Two U.S. aircraft carriers entered the flashpoint South China Sea for joint operations on Saturday, part of a concerted effort by Washington to reassure allies and partners in the region, and counter Beijing's moves in the disputed waterway.

The “dual carrier operations” involving the Yokosuka, Kanagawa Prefecture-based USS Ronald Reagan and the USS Nimitz, were confirmed by a spokesman for the Reagan. They come as China conducts its own large-scale military exercises near contested islands that it controls in the South China Sea’s Paracel chain. The Chinese exercises, which began Wednesday, were due to wrap up Sunday. It was not clear where the U.S. operations would take place.

A U.S. Navy spokesman said the carrier operations were being conducted to “support a free and open Indo-Pacific,” but were also likely intended to send a message to both Beijing — which Washington has labeled a "strategic competitor" — and regional partners.