The US military might deploy warships and surveillance aircraft near artificial islands being built by China to challenge Beijing's territorial claims in the South China Sea, officials said Wednesday.

But the US officials acknowledge such a move may fail to halt Beijing's massive land reclamation effort, recently dubbed China's "great wall of sand" by an American naval commander.

The Pentagon is weighing a range of options, including sailing destroyers or other naval ships within 12 nautical miles of the man-made islands, as well as flying P-3 and P-8 surveillance planes overhead, two defense officials told AFP.

The maritime and air patrols would be designed "to demonstrate support for freedom of navigation" and "to reassure our allies," said one official, who spoke on condition of anonymity.

"We have never recognized these artificial islands as legitimate claims," the official said.

"We see freedom of navigation as a fundamental, underlying principle that has to be upheld."

The Wall Street Journal first reported the options under consideration.

US officials admitted that China has been building at a rapid pace in recent years and that concerns expressed by the United States and regional governments so far have had little effect.

Last week, Pentagon officials revealed that China has been building artificial islands on top of coral reefs at an unprecedented pace. The rapid construction comes to 2,000 acres (800 hectares), with 75 percent of the total just in the last five months.

Washington is concerned China's increasingly assertive stance carries a military dimension that could undermine the sovereignty of neighboring nations and undercut America's naval and economic power in the Pacific.

However, China on Wednesday denounced any possible expansion in the US military's presence in the area.

"Freedom of navigation does not mean that the military vessels or aircraft of a foreign country can wilfully enter the territorial waters or airspace of another country," Chinese foreign ministry spokeswoman Hua Chunying told a regular briefing in Beijing.

China claims nearly all of the South China Sea, even waters approaching the coasts of its Asian neighbors.

The disputed waters are home to vital global shipping lanes and are believed to be rich in oil and gas.

Washington has flexed its military muscle previously to try to counter what it considers Beijing's aggressive moves.

Last November, two long-range B-52 bombers flew over China's newly-declared Air Defense Identification Zone (ADIZ) in the East China Sea.