US Defence Secretary Ash Carter has said that US aircraft carriers will be conducting more "freedom-of-navigation" operations in the South China Sea. However, he did not give any timeline for the operations.

Carter said that the US is putting its "best and newest" assets in the Asia-Pacific region to counter China's claim over South China Sea and Russia's provocation of the Baltic states. "We've done them before, all over the world. And we will do them again," the US Defence chief was quoted as saying by Reuters.

He added: "How China behaves will be the true test of its commitment to peace and security. This is why nations across the region are watching China's actions in areas like the maritime domain and cyberspace."

The rise in tension in the area is due to China's island-building projects in the region, he said. With more than $5tn (£3.2tn) in global trade passing through South China Sea every year, the Asian nation is claiming most of the area, but rival claims have been made by Malaysia, Vietnam, Philippines, Brunei and Taiwan.

"The United States joins virtually everyone else in the region in being deeply concerned about the pace and scope of land reclamation in the South China Sea," Carter stated at a defence forum at the Ronald Reagan Presidential Library in California. "The prospect of further militarization, as well as the potential for these activities to increase the risk of miscalculation or conflict among claimant states," he stressed.

"China has reclaimed more land than any other country in the entire history of the region," Carter concluded. He criticised Russia for violating Ukraine's sovereignty and for prolonging Syria's civil war, but claimed that it was possible for Russia to become a constructive player and end the conflict in Syria.