U.S. warns Beijing of South China Sea Islands

Pyongyang's accelerating nuclear and missile programmes are stoking fear in nearby Japan and prompting a harder line on North Korea from Prime Minister Shinzo Abe.

Mattis, speaking here at the Shangri-La Dialogue defense summit, said that the Trump administration is encouraged by China's "renewed commitment" to pressure North Korea to stop its nuclear weapons program, but that the United States will not accept China's military buildup in the South China Sea.

"China will not be a bystander in the nuclear issue", she said.

The United Nations Security Council has voted unanimously to expand sanctions against North Korea to include 14 more people and four organisations.

After pleading for China's cooperation to address Pyongyang's threat, Mattis warned Beijing that the USA will not accept its militarization policy in the South China Sea, whose sovereignty is also partially claimed by Vietnam, the Philippines, Malaysia, Brunei and Taiwan. "We can not and will not accept unilateral, coercive changes to the status quo".

Mr Fomin spoke at the Shangri-La Dialogue, an global security conference in Singapore attended by defence ministers and experts from 39 countries, including US Defence Secretary Jim Mattis.

"If the USA and its President continue to see allies and partners as purely transactional. that's going to put stress on relationships", said Ben Shreer, a defense analyst with the International Institute of Strategic Studies, the think-tank that organizes the defense conference.

"He was very clear, very strong", said Thornberry, who led a bipartisan congressional delegation on an Asia tour and attended Saturday's Singapore conference.

The U.S. has about 28,500 troops permanently based in South Korea, a defense treaty ally. "All states involved in territorial disagreements in the South China Sea need to adhere to the principle of the non-use of force", he said. "Our two countries can and do cooperate for mutual benefit. We will work closely with China where we share common cause".

"On May 29, the USA imperialists committed a grave military provocation by letting a formation of infamous B-1B nuclear strategic bombers fly over south Korea once again to stage a nuclear bomb dropping drill", said a statement from North Korea's state-run media outlet KCNA.

The analyst argued that the United States is trying to justify its military budget by introducing North Korea as an important threat. It allegedly works with a North Korean trading company, Tangun, which the US accuses of securing supplies for the nuclear program.

North Korea on Sunday slammed the latest round of United Nations sanctions as "mean" and vowed to press ahead with its missile and nuclear weapons programs.

North Korea accuses China and the U.S. of "railroading and enforcing" the latest round of sanctions "after having drafted it in the backroom at their own pleasure".

China appreciates these remarks made by the US secretary of defense, he added. "But other country can't be allowed to test or launch any object which goes with the words of nuclear or 'ballistic.' That is really the height of shameless arrogance, self-righteousness and double standards", the statement said.

It was Washington's "ultimate double standard" to ban other countries from nuclear or missile tests amid its own attempts to modernize the US arsenal.

"The United States will continue to adapt and continue to expand its ability to work with others to secure a peaceful, prosperous and free Asia, with respect for all nations upholding worldwide law", Mattis said to military leaders from at least 22 countries.

The North's Foreign Ministry "condemns and outrightly rejects the sanctions racket put forth by the United States and the U.N. Security Council to prevent the strengthening of our nuclear deterrence", a ministry spokesman said.