China is farther along in its development of a new stealth fighter jet than the U.S. had predicted, and that plane and other Chinese military advances are worrisome, U.S. Defence Secretary Robert Gates said Saturday.

"They clearly have potential to put some of our capabilities at risk," Gates said en route to military talks with Chinese leaders. "We have to pay attention to them, we have to respond appropriately with our own programs."

The United States has long known that China wanted to field a stealth jet, but development outpaced U.S. intelligence estimates, Gates said.