An editorial in Chinese newspaper Global Times, which is closely aligned to the country's ruling Communist party, condemned US "coercion."
"China mustn't tolerate rampant US violations of China's adjacent waters and the skies over those expanding islands," it read.
It went on to say that China's military should "be ready to launch countermeasures according to Washington's level of provocation."
Beijing has ignored calls from the United States to cease land reclamation projects in the South China Sea, where China's claims overlap with those of the Philippines, Vietnam, Malaysia, Brunei and Taiwan.
Washington suspects that Beijing plans to militarize the man-made islands, while China insists that they will serve a primarily humanitarian purpose.
Following a meeting of American and Australian officials on Tuesday, US Defense Secretary Ash Carter said that Washington will continue to send its military where international law allows, including the South China Sea.
Senior officials in Washington have indicated that the US military could sail by these islands in the coming days or weeks.
The warship or ships would pass within the 12-mile territorial limit China claims around the structures, to demonstrate that US commanders do not recognize it.
Such a move, the Global Times suggested, could be a "breach of China's bottom line."
"If the US encroaches on China's core interests, the Chinese military will stand up and use force to stop it," the paper warned.
On Wednesday, China's foreign ministry spokeswoman Hua Chunying said "certain countries have been flexing military muscles in the South China Sea over recent period of times.
"That is the biggest cause of 'militarization' in the South China Sea."