Defense Sec. Ash Carter Travels to South China Sea: Why His Visit Matters

— -- Secretary of Defense Ash Carter visited a U.S. aircraft carrier in the South China Sea on Friday, one day after announcing new military aid to the Philippines.

The nuclear-powered carrier, the USS John C. Stennis, was traveling about 60 miles west of the Philippines island of Luzon.

“What’s new is not an American carrier in this region,” Carter told troops on board, according to Reuters. “What’s new is the context of tension which exists which we want to reduce.”

Here's why Carter's visit matters.

What’s going on in the South China Sea?

China has been building ports, runways and radar facilities on several man-made islands in the South China Sea.

The seven new islands were constructed by dumping sand onto reefs, an effort by China to boost its claim to all of the Spratly Island chain in the South China Sea.

The Philippines, Malaysia, Vietnam, and Taiwan all claim to occupy portions of the Spratly Islands.

China’s development in the region is seen as threatening to other nations that occupy territory in that chain of islands to the east of Vietnam and west of the Philippines and Malaysia.

This area of the ocean is valuable because it contains fisheries and possible oil and gas reserves.

Why does this matter to the U.S.?

The U.S. sees China’s acts as raising tensions in the region and threatening U.S. allies, but senior officials have also said that the U.S. is not taking sides in the territorial disputes between China and other countries in the region.

Carter has repeatedly said that the U.S. does not want to see any country with a claim to the islands militarize the region and that the U.S. will continue to ensure its right of passage through international waters and airspace.

“We will fly, we will sail, we will operate everywhere international law permits in the South China Sea," Carter has said, which is why the U.S. Navy has recently conducted two “freedom of navigation” patrols that sailed within the 12-nautical mile territorial limits of some of the disputed islands.

China has said the U.S. is “militarizing” the South China Sea.

Why would Carter travel to the South China Sea?

Carter’s visit with the USS Stennis comes during his trip to India, the Philippines and the Middle East.

But it could also be in response to China’s announcement that one of its top military officers recently toured the islands in the South China Sea.

China said the official was overseeing construction on the islands, including in the Spratly region.

Carter previously visited the USS Theodore Roosevelt in the South China Sea last November.