US defence secretary Jim Mattis has said North Korea is a "clear and present danger" after the United Nations voted to expand sanctions against the state.
Speaking at an international security conference in Singapore, Mr Mattis also criticised China for what he described as coercive behaviour in the South China Sea.
His sharp words for both countries suggest he believes China will, out of self-interest, exert pressure on North Korea to halt its nuclear and missile programmes.
Mr Mattis said the Trump administration is encouraged by China’s renewed commitment to working with the US and others to rid North Korea of its nuclear weapons.
China blocked tough new sanctions against North Korea that the US pushed in the UN Security Council on Friday.
However, the council did vote unanimously to add 15 individuals and four entities linked to the North’s nuclear and missile programmes to a UN sanctions blacklist.
In his speech to the Shangri-La Dialogue, Mr Mattis sought to balance his hopeful comments on China with sharp criticism of what he called Beijing’s disregard for international law by its “indisputable militarisation” of artificial islands in disputed areas of the South China Sea.
“We cannot and will not accept unilateral, coercive changes to the status quo,” he said.
Overall, the speech by Mr Mattis struck a positive tone for co-operation and peace in the Asia-Pacific region, where he and his predecessors have made it a priority to nurture and strengthen alliances and partnerships.
“While competition between the US and China, the world’s two largest economies, is bound to occur, conflict is not inevitable,” he said.
However, he called North Korea an “urgent military threat”.
In a question-and-answer session with his audience of national security experts from across the globe, Mr Mattis was asked whether the US might attack the North pre-emptively and without warning South Korea in advance.
“We’re working diplomatically, economically, we’re trying to exhaust all possible alternatives to avert this race for a nuclear weapon in violation of ... the United Nations’ restrictions on North Korea’s activities,” he said.
"We want to stop this. We consider it urgent," he added. "As a matter of national security, the United States regards the threat from North Korea as a clear and present danger."
AP