The US is prepared to use force to prevent North Korea from becoming a nuclear-armed state, the country's ambassador to the UN says.

Speaking at an emergency UN Security Council meeting, ambassador Nikki Haley warned North Korea's regular missile launches were "quickly closing off the possibility of a diplomatic solution".

She said Pyongyang's test of a missile capable of reaching Alaska made the world "a more dangerous place", adding that the US would use its military to intervene "if we must".

Echoing President Trump's criticism of China, Ms Haley warned Beijing that it risked its trading relationship with the US unless it enforced UN sanctions on North Korea.

The US will propose new UN sanctions in the coming days, which Russia said it would oppose as they "will not resolve the issue".

Russian ambassador Vladimir Safronkov warned that military options were "inadmissible", adding that the UN was heading "towards a stalemate".

Meanwhile, China's UN ambassador Liu Jieyi said Beijing "has always been firmly opposed to chaos and conflict on the Korean peninsula", adding that military action was "not an option".

In response to Tuesday's launch, US and South Korean soldiers fired "deep strike" precision missiles into South Korean territorial waters.

Military officials said the launches were a show of force to demonstrate US-South Korean solidarity.

North Korea claimed its "landmark" Hwasong-14 missile is capable of carrying a "large, heavy nuclear warhead" that can withstand re-entry into the Earth's atmosphere.

It said the intercontinental ballistic missile reached an altitude of 2,802km and flew 933km for about 40 minutes before landing in the Sea of Japan.

Japan's data appeared to back up these claims, with the defence ministry claiming the altitude "greatly exceeded" 2,500km.

North Korean leader Kim Jong-Un reportedly oversaw the launch and said the projectile was "as handsome as a good-looking boy".

State media said he described the missile as a "gift" to the US "to help break their boredom".

Theresa May and Donald Trump are expected to discuss the test during the G20 summit in Hamburg on Friday.

Mrs May will say it is essential the international community is united in finding a peaceful solution "to the ongoing threat North Korea poses to international security", according to a senior Government official.