North Korea’s ability to launch a missile capable of reaching the US is advancing significantly and faster than expected, a top US army official has said.

US general Mark Milley, the chief of staff of the Army, cautioned that "time is running out” for a diplomatic solution to the North Korean crisis.

"North Korea is extremely dangerous and more dangerous as the weeks go by,” he said in remarks at the National Press Club in Washington DC.

The General pointed specifically to North Korea’s launch of an intercontinental ballistic missile (ICBM) earlier this month. Pentagon officials said at the time that the missile, which experts believe is capable of reaching Alaska, was something they had "never seen before".

While that missile is likely not capable of transporting a nuclear warhead, the Pentagon has warned that it could become nuclear-capable as early as 2018 – two years earlier than originally predicted. Pentagon officials moved the timeline up in light of the shocking 4 July missile test.

In the wake of that test, US Ambassador to the UN Nikki Haley said America is prepared to use military force against North Korea if necessary.

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

In pictures: North Korea military drill Show all 8 1 /8 In pictures: North Korea military drill In pictures: North Korea military drill North Korea's leader Kim Jong Un watches a military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) is seen in this handout photo by North Korea's Korean Central News Agency (KCNA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) is seen in this handout photo by North Korea's Korean Central News Agency (KCNA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video

In testimony before the Senate Armed Services Committee earlier this year, Mr Milley warned that war with North Korea would be “tragic on an unbelievable scale”.

“The levels of violence would be immense, the likes of which the world hasn’t seen since the Second World War,” he said.

The US is currently testing non-military strategies for containing the North Korean threat, including imposing new economic sanctions. A bill passed earlier this week by the House of Representatives would impose fresh sanctions on the country for their ICBM programme.

President Donald Trump has prioritised working with China to solve the crisis, but progress has been mixed.

Earlier this month, upon learning that trade between China and North Korea had grown in the last quarter, the US president tweeted: “So much for China working with us - but we had to give it a try!”

Just days later, however, he boasted: “Just left China’s President Xi where we had an excellent meeting on trade & North Korea.”