A top U.S. official on Thursday said China's land reclamation and militarization in the disputed South China Sea was raising tensions and serious questions about its intention.
On a visit to Vietnam, U.S. Deputy Secretary of State Antony Blinken said Washington would continue to play a constructive role in supporting its regional allies but was not looking to set up bases for its troops.
"United States and Vietnam are sharing interest in maintaining peace and stability in the region, so is China," Blinken said in a speech at a Hanoi university.
"But its massive land reclamation projects in the South China Sea and the increasing militarization of these outposts fuels regional tension and raises serious questions about China's intention," Blinken said.
Blinken also called on China, and all nations, to respect an upcoming decision by an international arbitration court in a case brought by the Philippines that could dent China's claim to nine-tenths of the South China Sea.
Similar comments by Hugo Swire, British minister of state responsible for East Asia, angered China earlier this week.
Beijing claims virtually all of the South China Sea and rejects the court's authority in the case, which numerous experts believe will go in favor of the Philippines, potentially raising tensions in the strategic waterway.
"The United States will defend our national interests and support our allies and partners in the region," said Blinken.
"We are not looking for bases but we will continue to sail, to fly, to operate anywhere that international law allows."
More than $5 trillion of world trade is shipped through the South China Sea every year. Apart from China's territorial claims there, Brunei, Malaysia, the Philippines, Taiwan and Vietnam have rival claims.