BOSTON (REUTERS) - US Secretary of State John Kerry and Defence Secretary Ash Carter met their Australian counterparts in Boston on Tuesday to discuss expanded cooperation in the South China Sea and possible US patrols within 12 nautical miles of artificial islands built by China.
China has claimed most of the South China Sea and last week its foreign ministry warned that Beijing would not stand for violations of its territorial waters in the name of freedom of navigation.
A senior US official said the issue of patrols would be discussed at the meeting.
The two countries, close treaty allies, are due to sign an agreement on expanded defence cooperation during the talks with Australian Foreign Minister Julie Bishop and Defence Minister Marise Payne.
"We do operate with the Australians in certain areas of the South China Sea," the official said.
"And we're looking for ways of expanding the opportunities for us to operate together."
The official declined comment on reports that the United States had already decided to conduct freedom-of-navigation operations inside 12 nautical mile limits that China claims around islands built on reefs in the Spratly archipelago.
"You know, doing the 12 nautical mile challenge is one among a variety of options that we're considering, but I can't get into current or future operations," he said.
"We're waiting for an interagency decision that includes the White House."
President Barack Obama said during a visit by China's President Xi Jinping to the United States last month that "the United States will continue to sail, fly and operate anywhere that international law allows."
Some analysts in Washington believe the decision has been taken and the patrols could take place later this week or next.
They are likely to provoke protests from China.
Mira Rapp Hooper, a senior fellow at the Asia-Pacific Security Programme at the Centre for a New American Security, said she expected the patrols to be carried out at islands occupied by other claimants, such as Vietnam.
Greg Poling of the Asia Maritime Transparency Initiative at the Centre for Strategic and International Studies said he expected they would be conducted "only around those features that were indisputably below water at high tide before the reclamation started and are too far from any rocks to fall within their territorial sea."
In the case of China, this meant Mischief and Subi reefs in the Spratly archipelago, he said.
The United States has argued that under international law building up artificial islands on previously submerged reefs does not entitle a country to claim a territorial limit and that it is vital to maintain freedom of navigation in a sea through which more than US$5 trillion (S$7 trillion) of world trade passes every year.