BEIJING — The Pentagon is stepping up investments in a range of weapons, jet fighters and technology in response to the Chinese military buildup in the Pacific, Defense Secretary Robert M. Gates said Saturday on the eve of his visit to Beijing.

Despite billions of dollars in proposed Pentagon budget cuts that Mr. Gates announced this past week, he said that the Chinese development of its first radar-evading fighter jet, as well as an antiship ballistic missile that could hit American aircraft carriers, had persuaded him to make improvements in American weaponry a priority.

“They clearly have potential to put some of our capabilities at risk, and we have to pay attention to them, we have to respond appropriately with our own programs,” Mr. Gates said.

At the same time Mr. Gates doused China’s proud rollout this past week of its new stealth fighter jet, the J-20, saying that even though it was a matter for concern, there “is some question about just how stealthy” it is.