Singapore, Jun 3 (IANS): US Defence Secretary James Mattis on Saturday urged China to act against North Korea's nuclear programme and warned that Washington will not accept Beijing's militarization in the disputed South China Sea.

Speaking at the Shangri-La Dialogue, Asia's annual defence summit here, Mattis called North Korea's nuclear programme and ballistic missile tests as the "most urgent threat" to peace and stability, Efe news reported.

According to Mattis, President Donald Trump's administration considers China's commitment to the shared goal of denuclearisation on the Korean peninsula encouraging, but urged Beijing to act.

"It is therefore imperative that we do our part each of us to fulfil our obligations and work together to support our shared goal of denuclearisation on the Korean Peninsula," he said.

After pleading for China's cooperation to address Pyongyang's threat, Mattis warned Beijing that the US 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 oppose countries militarizing artificial islands and enforcing excessive maritime claims unsupported by international law. We cannot and will not accept unilateral, coercive changes to the status quo," Mattis added.