US Secretary of State John Kerry on Wednesday slammed China for its increased "militarization" in the strategically important South China Sea, after Taiwan said Beijing deployed surface-to-air missiles on a disputed island there.
"There is every evidence, every day, that there has been an increase of militarization of one kind or another. It's of a serious concern," Kerry told reporters.
Fox News first reported missile launchers and a radar system had arrived on Woody Island, part of the Paracels chain, in the past week. Taiwan's defense ministry later confirmed the facility's existence.
Beijing has controlled all of the Paracels, which are also claimed by Hanoi and Taipei, since seizing several from South Vietnam in a brief, bloody battle towards the end of the Vietnam War.
But tensions in the sea -- through which one-third of the world's oil passes -- have mounted in recent months since China transformed contested reefs in the Spratly islands further south into artificial islands capable of supporting military facilities.
Washington says the move threatens free passage in a strategically vital area and has sent warships to sail close to the disputed islands to assert freedom of navigation, raising fears of escalation.
"We have said repeatedly with respect to China that the standard that should be applied to all countries with respect to the South China Sea is no militarization," Kerry said.
The secretary of state recalled that when Chinese President Xi Jinping came to Washington late last year, "he stood in the Rose Garden with President (Barack) Obama and said China will not militarize in the South China Sea."
"We had these conversations with the Chinese and I'm confident that over the next days, we will have further very serious conversations on this," Kerry said.
He said he hoped that Beijing would work to resolve the maritime disputes "not through unilateral action, not through force, not through militarization but through diplomacy and by working with other countries and claimants."
On Tuesday, Obama called for "tangible steps" to lower tensions in the South China Sea.
Beijing meanwhile has insisted it has the right to build "self-defense" systems in the region.