The head of the US armed forces in the Asia-Pacific, Admiral Timothy Keating, said he was told by Chinese leaders during a visit to Beijing that its so-called 'area denial weapons' were 'to protect those things that are ours.'

But he said, "we find it troubling that the capabilities of some of these weapons systems would tend to exceed our own expectations for protecting those things that are 'ours'."

Keating said the United States had "intelligence that reinforces my opinion that China is developing, fielding and has in place weapons that could be characterized as having, amongst perhaps other purposes, an ability to restrict movement in and around certain areas on the sea, in the air or under the sea."

"I'll go back to the point we made a couple of times already - that we understood PRC (China's) intentions, not just their transparency, not just the fact that these weapons exist. We know they exist," he said.

"It's why are they being fielded," Keating asked, speaking at a Washington forum of the US-based Asia Society.

The Pentagon fears China's area-denial arms, including missiles, can be used to attack US aircraft carriers and ships, reports have said.