US Navy destroyer sails past Beijing's man-made island in the South China Sea for the SECOND time this year

On Sunday, Pentagon sent the USS Stethem to Triton Island in South East Asia
China, Taiwan and Philippines all claim Triton but China has built a base on it
US sailed within 12 miles of the island - within waters China claims as its own
It was trailed by a Chinese warship while it completed its international mission
The operation was to emphasize that the waters are international, not territorial
In May the US ran a similar voyage to one of China's man-made islands in the sea
s

For the second time in just over two months, the US has challenged China's claim to the South China Sea and a number of disputed islands within it.

On Sunday the Pentagon sent a destroyer, the USS Stethem, to sail close to the shore of Triton Island - one of a number in the Paracel Island chain that China claims ownership of.

In response, China trailed the US destroyer with one of its own warships, two US defense officials told Fox News.

Voyage: On Sunday the USS Stethem (pictured) a US destroyer, sailed within 12 miles of an island claimed by China in the South China Sea, to establish its waters as international

Denied: Triton Island (pictured) is claimed by China (which has built a base, far left). By sailing through the waters it claims to own, the US denied the country's ownership of the island

According to international law, countries' territories extend 12 miles out from their shores.

So by sailing within that distance of Triton, the Stethem dismissed China's claim to both the island and the waters around it.

The US calls these voyages 'freedom of navigation operations' or FONOPS, because they are intended to reinforce the territories as international waters.

Although China has constructed a base on the island to reinforce its claim, both Taiwan and the Philippines say they are the rightful owners of the island.

The Pentagon said that it was challenging those countries' claims to the island too. Washington is particularly concerned about China placing ground-to-air missiles on the chain.

Lt Cmdr Matt Knight, a spokesman for the US Pacific Fleet, would not confirm the operation.

But he did say: 'We conduct routine and regular FONOPs, as we have done in the past and will continue to do in the future.'

Disputed: Triton Island is located in the South China Sea and its ownership is disputed as it is claimed by China, Taiwan and Vietnam. The US said it was denying all claims to the island

Triton is a naturally occurring island, and not one of the several manufactured islands built by China in the area to lay claim to the seas there.

This is the second FONOP to be conducted under the Trump administration.

In May the USS Dewey, another destroyer, sailed six miles from one of China's man-made islands in the South China Sea.

It made the unusual decision to stop within that water and conduct a 'man overboard' training exercise.

That was a bolder move than in previous missions, in which the ships had sailed past without stopping.

Sunday's operation comes at a difficult time in America-Sino relations. The US had been talking to China about trying to curb North Korea's nuclear development, but Trump tweeted that effort had failed last month.

On Friday the US unveiled new sanctions against a Chinese bank that had been trading with North Korea.

Treasury Secretary Steven Mnuchin said the move was not a punishment for China's failure to rein in North Korea, and was focused on a single bank.

Tough times: The US and China have a difficult relationship at the moment. Last month Donald Trump tweeted that China had failed to curb North Korean missile development. Last week the US placed sanctions on a bank dealing with North Korea but denied that it was punishing China

The day before, America confirmed a $1.4 billion arms deal with Taiwan, which has opposing claims to a number of South China Sea islands, and also claims that it is the rightful government of mainland China.

China's claim to Triton Island was previously challenged just over a year ago, on January 30, 2016, when the USS Curtis Wilbur, another destroyer, was sent within 12 miles of the island.

The Pentagon again said the mission was done to secure the sea around the island as international waters.

China denounced the voyage as 'intentionally provocative' and 'irresponsible and extremely dangerous,' and said it had taken 'relevant measures including monitoring and admonishments.'

Operation: In May the USS Dewey (pictured), another destroyer, sailed within six miles of an artificial island in the South China Sea, again denying China's ownership of waters there