CAMP RED CLOUD, South Korea - The top US military officer criticised China on Wednesday for cutting off military contacts with the United States, saying dialogue could help dispel concerns over Beijing's arms buildup.

Speaking to US troops in South Korea, Admiral Mike Mullen said China's spending on hi-tech weaponry, including anti-ship missiles, had raised questions about its intentions in the region.

But he said the absence of a regular dialogue with China's military made it difficult to address those concerns.

"It's really important that we know each other in ways that we just don't right now because our engagement with them is very much off-and-on," Mullen told troops from the US Army's 2nd Infantry Division at Camp Red Cloud.

He said every country had a right to bolster its armed forces.

"But it's the specifics of some of it, that you know I'd like to have a conversation to see where they're going. Right now I can't do that."

China suspended military relations in January after Washington unveiled a 6.4 billion dollar arms package for Taiwan. And in May, China rebuffed a planned visit to Beijing in June by US Defense Secretary Robert Gates.

China opposes any arms sales to Taiwan, which it regards as part of its territory awaiting reunification, even though the two sides have been split since the end of a civil war in 1949.

Mullen said China's military had made "a fairly significant investment in high-end equipment" including satellites, aircraft, anti-ship missiles and a planned aircraft carrier group.

He called the move a "strategic shift, where they are moving from a focus on their ground forces to focus on their navy, and their maritime forces and their air force".

He added: "I have moved from being furious about what they're doing to being concerned about what they're doing."

US officials worry that China's more assertive stance in the Pacific Ocean and its anti-ship missile arsenal, capable of striking aircraft carriers, could undercut American naval power in the region.

Mullen's comments came a day after he defended plans for joint US-South Korean naval exercises in the Yellow Sea in coming months, despite misgivings in China.

The four-star admiral said the US Navy reserved the right to operate in international waters and had been holding drills for years in the Yellow Sea, which separates China from the Korean peninsula.