China will intensify its vigilance, but not lash back, after the United States announced it will shift most of its warships to the Asia-Pacific region by 2020, media reported on Sunday.

People's Liberation Army (PLA) Lieutenant General Ren Haiquan's comments were Beijing's first public reaction to the statement on Saturday by U.S. Defense Secretary Leon Panetta that the Pentagon will reposition its naval fleet so 60 percent of its battleships are in the Asia-Pacific by the end of the decade, up from about 50 percent now.

"First, we should not treat this as a disaster," said Ren, who is leading the Chinese delegation to the regional security dialogue in Singapore where Panetta also announced the shift.

"I believe that this is the United States' response to its own national interests, its fiscal difficulties and global security developments," Ren said in comments reported by Hong Kong's Phoenix Television.

Beijing has long been wary of U.S. intentions, with more hawkish voices in the PLA saying that Washington is bent on encircling China and frustrating its rise.

Ren, who is a vice president of the Chinese Academy of Military Sciences, which helps shape PLA strategy, said Beijing would not be complacent about U.S. moves.

"The second sentence (of my response) is that we should not treat this indifferently," Ren said, according to Phoenix.

"We must see that we're facing extremely complex and one could sometimes even say quite serious developments, and we must raise our awareness of peril, and prepare to cope with all kinds of complex and serious circumstances."

China's fast-modernizing navy has stirred worries among neighbors, including in southeast Asia, where several countries are in dispute with Beijing over rival territorial claims in the South China Sea.

Under the plans Panetta announced, the U.S. Navy would maintain six aircraft carriers assigned to the Pacific. Six of its 11 carriers are now assigned to the Pacific, but that will fall to five when the USS Enterprise retires this year.

The number will return to six when the new carrier USS Gerald R. Ford is completed in 2015.

The U.S. Navy had a fleet of 282 ships as of March. That is expected to slip to about 276 over the next two years before beginning to rise toward the goal of a 300-ship fleet, according to a 30-year Navy projection released in March.

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