The US needs to clarify the reported remarks by a US official on the issue and that countries should avoid "risky and provocative approaches to maintain the regional peace and stability," Foreign Ministry spokeswoman Hua Chunying said.
She was reacting to US official's remarks that the Pentagon was exploring options of sending Navy surveillance aircraft and vessels to "assert freedom of navigation" around the islands China has rapidly built recently to reinforce its claims in the strategically vital region.
"But freedom of navigation does not give one country's military aircraft and ships free access to another country's territorial waters and airspace," she said.
Hua said China will resolutely safeguard its territorial sovereignty and urged the US not to take any risks or make any provocations so as to maintain regional peace and stability.
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"We express serious concern about the US remarks," Hua told reporters at a news briefing.
China claims virtually all of the South China Sea, even waters approaching the coasts of its Asian neighbours, and has provoked alarm with increasingly bold actions.
The disputed region is also claimed by Malaysia, the Philippines, Vietnam, Brunei and Taiwan.
The US military already operates in the South China Sea, But crossing the 12 nautical mile territorial limit around the islands could raise tensions if China chose to respond.
Last week, an alarmed US accused China of reclaiming up to 800 hectares of land to build artificial islands in the Spratlys -- an archipelago of more than a hundred islands, reefs and atolls between Vietnam and the Philippines.
But China defends the reclamation, saying it is Beijing's territory and that the infrastructure are for public service use.