The US and China are working on a “range of options” on North Korea, the US top security adviser has said, as tensions mount over the country’s nuclear and missile programmes.
Lt Gen HR McMaster told ABC News there was consensus with China that this was a “situation that just can’t continue”.
The comments come after a failed missile test launch by North Korea and a massive military parade.
President Trump had earlier said China was “working with us” on the issue.
Beijing, Pyongyang’s biggest ally, has been under pressure by Washington to exert more pressure on its neighbour.
Sunday’s comments appear to be the first confirmation that both countries are working together on how to deal with the North Korean issue.
President Xi Jinping offered co-operation on “communication and co-ordination” in his meeting with Mr Trump last week, the BBC’s Robin Brant in Shanghai reports.
Gen McMaster, who was in the Afghan capital, Kabul, said the US would respond “in the best interest of the American people”.
“The president has made clear that he will not accept the United States and its allies and partners in the region being under threat from this hostile regime with nuclear weapons,” he said.
Earlier, South Korean and US military officials said a North Korean missile had detonated soon after launch. The US Pacific Command said it believed to be a ballistic missile.
One unnamed US official said it was unlikely to have been an intercontinental (ICBM) missile, but investigations were continuing.
Ballistic missiles follow high trajectories and are initially powered and guided, but fall to their target under gravity. ICBMs follow a sub-orbital trajectory, others stay within the atmosphere.