File Photo: South China Sea.
The United States and its Pacific ally Australia warned China on Tuesday that they remain committed to freedom of navigation in the waters of the South China Sea.
China has maritime territorial disputes with several of its southeast Asian neighbors and is trying to bolster its claim by building artificial islands.
According to senior US officials, speaking on condiction of anonymity, Washington is drawing up a plan to 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.
Meanwhile, after an annual two-day meeting, the US and Australian defense and foreign ministers said they do not have a view on the legal arguments of the dispute.
But they warned that they will continue to support freedom of navigation and send ships and planes through what they regard as internationals water in the region.
US Defense Secretary Ash Carter, joined Secretary of State John Kerry and their Australian counterparts Marise Payne and Julie Bishop in Boston.
"Australia and America both want to sustain and renew an Asia-Pacific regional security architecture where everyone rises and everyone prospers," Carter said.
"But make no mistake," he warned "the United States will fly, sail and operate wherever international law allows, as we do around the world.
"And the South China Sea is not and will not be an exception."
Carter said this was not just a US commitment, but was shared by Washington's major regional allies Japan, the Philippines, India and Vietnam.
Bishop said Washington and Canberra were "on the same page" over the dispute.
"We do not take sides on the various territorial claims, but we urge all parties to not act unilaterally, to not act in a way that would escalate tensions," she said.
Bishop expressed support for "the principles of freedom of navigation and freedom of overflight."
"We continue to work together to press those principles on all claimants in the South China Sea and elsewhere," she added.
On Saturday, China vowed to continue building on the disputed reefs and said construction had finished on two lighthouses in areas claimed by smaller rivals.
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.
Chinese President Xi Jinping has said Beijing will not militarize its new structures, but satellite images show they have runways that could be used by air force jets.