Chinese media slammed the US Thursday for "ceaseless provocations" in the South China Sea, with Washington expected to soon send warships close to artificial islands Beijing has built in disputed waters.
Tensions have mounted since China transformed reefs in the area -- also claimed by several neighbouring countries -- into small islands capable of supporting military facilities, a move that the US says threatens freedom of navigation.
Following a meeting of American and Australian officials Tuesday, US Defence Secretary Ash Carter warned Beijing that Washington will continue to send its military where international law allows, including the South China Sea.
The remarks were backed by Australian Foreign Minister Julie Bishop, who said the two countries are "on the same page."
An editorial in The Global Times, which is close to China's ruling Communist party, condemned Washington's "ceaseless provocations and coercion".
"China mustn't tolerate rampant US violations of China's adjacent waters and the skies over those expanding islands," it said, adding that its military should "be ready to launch countermeasures according to Washington's level of provocation," it added.
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 recognise 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.
The editorial came after China's foreign ministry spokeswoman Hua Chunying told reporters that "certain countries have been flexing military muscles in the South China Sea over recent period of times".
"That is the biggest cause of 'militarisation' in the South China Sea,” she added at a regular briefing Wednesday.
On Saturday, China said work had finished on two lighthouses in the disputed area and pledged to build more facilities, which it says are intended to serve civilian as well as military purposes.
Satellite images of the islands published by a Washington-based think tank show runways that could be used by air force jets.
Brunei, Malaysia, the Philippines and Vietnam -- members of the Association of Southeast Asian Nations (ASEAN) -- claim parts of the sea. Taiwan is a sixth claimant.
China has invited ASEAN defence ministers for a two-day informal summit in Beijing starting Thursday, according to the country's defence ministry.