USA and Chinese forces are confronting one another in the South China Sea with increasing regularity, as Washington exerts pressure on Beijing's aggressive territorial claims.
Mattis said the USA just has to learn how to manage its relationship with the communist nation.
The two ships could have been seconds away from a collision, said Carl Schuster, a former US Navy captain with 12 years at sea who looked at the photos at the request of CNN. They spoke on condition of anonymity to discuss internal planning.
He said that China now spends as much on its military as the rest of Asia combined, and is prioritizing capabilities to erode United States military advantages "on land, at sea, in the air, and in space".
The US and China have clashed over a wide range of issues, including trade,Taiwan, sanctions, and increased American military activity in the disputed South China Sea, which China and other Asian nations hold certain claims to.
The Chinese warship moves ahead of its U.S. counterpart after forcing the U.S. ship to perform a "radical maneuver", Schuster said.
China also protested a recent mission by nuclear-capable U.S. B-52 bombers over the disputed South China Sea, calling the flights "provocative".
The US Pacific Fleet says a US Navy ship had to manoeuvre to prevent a collision with a Chinese destroyer in the South China Sea that came aggressively close.
A Chinese warship came perilously close to colliding with a United States Navy destroyer in the South China Sea on Sunday. The onus would be on the Chinese ship to keep safe distance from and maneuver past the United States ship.
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A strategic waterway, Beijing has strengthened its military presence in the South China Sea by building islands there and placing airfields and missiles on them.
At the center of the tensions is a growing U.S.
The vice president cited U.S. intelligence agencies but offered no evidence to back up his claims, which are likely to inflame relations between Washington and Beijing, already at their lowest point in years thanks to the burgeoning trade war, policy differences and U.S. allegations of political interference.
Mattis characterized China's militarization in the South China Sea as being for "intimidation and coercion".
"Taiwan's embrace of democracy shows a better path for all the Chinese people", Mr. Pence will say, while adding that the U.S.
The pictures were taken by a U.S. Navy aircraft but were posted online by the blog.
"I just think it's part of reality", Mattis said Monday.
US Navy guided-missile destroyers and guided-missile cruisers. We have various issues: diplomatic, economic, security.