U.S. Defense Secretary Jim Mattis on Saturday raised the prospect of additional American steps against China if its "militarization" of the South China Sea keeps apace.
"We do not do freedom of navigation for America alone, we do freedom of navigation for all nations", Mattis said.
The U.S., he said, "will continue to pursue a constructive, results-oriented relationship with China, cooperation when possible, and competing vigorously where we must".
The U.S. Navy on Sunday conducted the latest of its "freedom of navigation" patrols near China-occupied features to demonstrate the right to sail through what it considers to be global waters.
"Despite China's claims to the contrary, the placement of these weapon systems is tied directly to military use for the purposes of intimidation and coercion", he said.
Mattis's comments came at a time of increased tensions between the USA and China, with the two countries locked in an ongoing trade dispute while Beijing has also continued to assert its territorial claims in the South China Sea.
In a meeting with former President Barack Obama during a visit to the United States in 2015, China's President Xi Jinping denied the country had plans to establish military strongholds in the South China Sea.
The remarks come amid growing discord between China and the U-S over the disputed waters and islands.
U.S. Secretary of Defense Jim Mattis arrives to give an address at the Shangri-la Dialogue in Singapore, June 2, 2018.
While the operation had been planned months in advance, and similar operations have become routine, it comes at a particularly sensitive time and just days after the Pentagon disinvited China from a major US-hosted naval drill.
Top North Korean official meets Trump at White House
Experts agree that a meeting between Kim and Trump would legitimize a pariah nation and grant North Korea a long-term wish. In the meeting, Lavrov invited Kim Jong Un to visit Russia and meet with the Russian President Vladimir Putin .
China believes islands, islets and other maritime features in the South China Sea are its sovereign territory and that it is within its rights to build defenses on them.
"I believe there are much larger consequences in the future when nations lose the rapport of their neighbours. eventually these (actions) do not pay off", Mr Mattis said.
Speaking at a high-profile security summit in Singapore 10 days before President Donald Trump is due to meet North Korean leader Kim Jong Un, the Pentagon chief also said the U.S. military continues to support diplomats pushing for the "complete, verifiable and irreversible" denuclearization of the Korean peninsula (see story on D1).
"The Chinese people and the Chinese government will never allow any person, any political party and any organisation under any name to separate any piece of Chinese territory from China at any time and in any form", Mr He said. China claims Taiwan as its own and it is one of its most sensitive issues.
President Donald Trump talks with Kim Yong Chol, former North Korean military intelligence chief and one of leader Kim Jong Un's closest aides, as they walk from their meeting in the Oval Office of the White House in Washington, June 1, 2018.
Delegates hoping for clarity on Trump's intentions for a scheduled June 12 summit with North Korean leader Kim did not get much from Mattis, though he said the issue of the permanent deployment of about 28,5000 USA troops in South Korea will not be "on the table". "This is our priority theater", Mattis added.
On the Trump administration's relations with US allies and neighbors, including the recent move to place tariffs on Canada, Mexico, and the European Union, Mattis acknowledged there had been "some unusual approaches".
South Korea and Japan have expressed concern that Trump may put USA security interests ahead of theirs in pursuing a deal with North Korea.
"I believe that it is important not to reward North Korea exclusively for agreeing to have a dialogue", Onodera said, noting that Pyongyang has made denuclearization promises in the past, only to backtrack.
He said the only way to bring peace in the region was to ensure North Korea take concrete actions to end all nuclear programmes and ballistic missiles of all ranges.
"We are focused on modernising our alliance with both Republic of Korea and Japan, transforming these critical alliances to meet the challenges of the 21st-century", Mattis said.