Foreign Ministry spokeswoman Hua Chunying told reporters China won't remain passive if its interests come under attack.
"I would like to stress again that China's determination to defend national sovereignty and its legitimate rights and interests is unswerving," Hua said. "We will adopt stern measures to counter any acts that will pose provocations and threats against China."
Beijing this week responded angrily to a Wall Street Journal report which cited anonymous U.S. Officials saying that Washington is considering sending military ships and planes to challenge Chinese claims to islands it is building in the South China Sea.
American officials say Kerry will carry a message that China's large-scale land reclamation and general behavior in the South China Sea will hurt China's image and foreign relations, including with the US.
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His visit on Saturday will also set the stage for annual US-China economic and strategic talks this summer and a trip to the US by Chinese President Xi Jinping in the fall.
"The Cold-War mentality, which is prone to the use of force to resolve disputes, is already outdated," Cui said. It's not clear whether or when the US might begin sending planes and ships within the 12 nautical mile territorial limit surrounding China's island claims or how exactly Beijing might respond.
However, the littoral combat ship USS Fort Worth and its MH-60R Seahawk helicopter conducted patrols in seas and airspace near the Spratlys this month, a first for a ship of that class, the Navy said in a report on its website. During the patrols, the ship encountered several Chinese navy warships and communicated with them using an agreed set of protocols to avoid misunderstandings, it said.