The chief of US naval operations spoke with his Chinese counterpart via video on Thursday, two days after a US destroyer sailed close to artificial islands built by Beijing in the South China Sea.

The call between Admiral John Richardson and Admiral Wu Shengli, who commands the Chinese navy, lasted about an hour.

Pentagon spokesman Captain Jeff Davis said the men discussed "freedom of navigation operations, the relationship between the two navies including pending port visits, senior leader engagement and the importance of maintaining an ongoing dialogue."

Navy spokesman Lieutenant Tim Hawkins said the conversation was "professional and productive."

The USS Lassen guided missile destroyer sailed within 12 nautical miles of at least one of the land formations claimed by China in the disputed Spratly Islands chain on Tuesday.

The move infuriated Beijing, which summoned the US ambassador and denounced what it called a threat to its sovereignty.

Davis said the sailing was not intended as a challenge to the sovereignty of "land features" in the South China Sea.

The "US takes no position in competing sovereignty claims," he said.

Wu and Richardson agreed to speak again via video conference later this year, he added.

Tensions have mounted since China transformed reefs in the area -- also claimed by several neighboring countries -- into small islands capable of supporting military facilities, a move the US says threatens freedom of navigation.

Washington has repeatedly said it does not recognize Chinese claims to territorial waters around the artificial islands.

A US official told AFP on Tuesday that the US Navy would send more warships to sail close to the controversial islets.

Russian warplanes intercepted near US carrier off Korean peninsula
Washington (AFP) Oct 29, 2015 - Fighter jets from South Korea and the United States intercepted two Russian warplanes after they flew near a US aircraft carrier operating off the Korean peninsula, officials said Thursday.

White House spokesman Josh Earnest said the USS Ronald Reagan -- a massive, nuclear-powered supercarrier -- was involved in a military exercise with South Korean partners when two Russian Tu-142 Bear aircraft flew past the ship.

"These Russian aircraft were intercepted first by Korean military aircraft that were operating in the region," Earnest said. Four American F/A-18s were then mobilized.

Earnest sought to downplay the incident in the Sea of Japan (East Sea), calling it "not a particularly threatening encounter" and noted that the USS Ronald Reagan was operating in international waters at the time.

"This is a particular situation that did not result in a significant confrontation," he said.

The two Russian Tu-142 Bear aircraft were flying about a mile from the carrier at an altitude of 500 feet (150 meters) on Tuesday, Pentagon spokesman Captain Jeff Davis said.

He said there was no evidence the Russian planes posed a direct threat. Tu-142 Bears are primarily reconnaissance and anti-submarine aircraft.

Still, the carrier scrambled four F/A-18 fighters to intercept and escort the Russian aircraft, he said.

One of the US ships accompanying the USS Ronald Reagan tried to hail the Russian aircraft by radio but did not receive a response, he added.

"It's standard operating procedure for US planes to escort any aircraft that are flying anywhere in the vicinity of US Navy ships," Davis said. "The interaction was characterized as safe."

"Any time there are aircraft that are operating in close proximity to a US Navy ship, particularly an aircraft carrier, we are going to take action to launch and make sure we are tracking it very closely," Davis said.

He said this kind of incident is not unprecedented, noting: "It doesn't happen frequently but this did occur."

The incident comes after Russia and the United States on October 10 signed a memorandum of understanding that establishes protocols for pilots flying over Syria.

Both Russia and a US-led coalition are conducting separate bombing campaigns in the war-torn country. Though they are mainly operating in different regions, officials are worried about planes crashing into each other in the sky.