he US has warned it is ready to use force "if we must" to stop North Korea's nuclear missile program but says it prefers global diplomatic action against Pyongyang for test-launching an intercontinental ballistic missile.

The US ambassador to the United Nations, Nikki Haley, told a UN Security Council meeting that North Korea's actions were "quickly closing off the possibility of a diplomatic solution" and the US was prepared to defend itself and its allies.

"One of our capabilities lies with our considerable military forces. We will use them if we must but we prefer not to have to go in that direction," Haley said on Wednesday.

She urged China, North Korea's only major ally, to do more to rein in Pyongyang.

Taking a major step in its missile program, North Korea on Tuesday test-launched a Hwasong-14 missile it says could carry a large nuclear warhead.

Some experts believe it has the range to reach Alaska and the Pacific northwest of the US.

North Korean leader Kim Jong Un said the test completed his country's strategic weapons capability that also includes atomic and hydrogen bombs, according to the state KCNA news agency.


Pyongyang will not negotiate with the US to give up those weapons until Washington abandons its hostile policy against the North, KCNA quoted Kim as saying.

US President Donald Trump has frequently urged China to press the isolated country's leadership to give up its nuclear program.

Haley said the US would propose new UN sanctions on North Korea in coming days and warned if Russia and China did not support the move then "we will go our own path".

Diplomats say Beijing has not been fully enforcing existing sanctions on its neighbour and has resisted tougher measures such as an oil embargo, bans on the North Korean airline and guest workers, and measures against Chinese banks and other firms doing business with the North.

China's UN ambassador, Liu Jieyi, told the Security Council the missile launch was a "flagrant violation" of UN resolutions and "unacceptable".

"We call on all the parties concerned to exercise restraint, avoid provocative actions and belligerent rhetoric, demonstrate the will for unconditional dialogue and work actively together to defuse the tension," Liu said.

Russia's deputy UN envoy, Vladimir Safronkov, said military force should not be considered and called for a halt to the deployment of a US missile defence system in South Korea.

He also said attempts to strangle North Korea economically were "unacceptable" and sanctions would not resolve the issue.

Trump and other leaders from the G20 meeting in Germany this week are due to discuss steps to rein in North Korea's weapons program.