Donald Trump has taken a swipe at North Korean dictator Kim Jong Un, labelling him 'Rocket Man' following the secretive state's controversial missile tests.

On Twitter, the US leader said: "I spoke with President Moon of South Korea last night. Asked him how Rocket Man is doing. Long gas lines forming in North Korea. Too bad!"

I spoke with President Moon of South Korea last night. Asked him how Rocket Man is doing. Long gas lines forming in North Korea. Too bad! — Donald J. Trump (@realDonaldTrump) September 17, 2017

President Trump's comments suggested increased sanctions recently passed by the UN restricting its gas and oil imports were having a noticeable effect.

Mr Kim has vowed to complete his nation's nuclear programme.

The US Ambassador to the United Nations said on Sunday that sanctions were the UN's last option for containing that programme.


"We have pretty much exhausted all the things that we can do at the Security Council at this point," ambassador Nikki Haley told CNN.

Ms Haley said she was perfectly happy to hand the issue over to the US Defence Secretary, James Mattis.

Trump's frank talk on North Korea and IS

Speaking at a White House news conference earlier this week, the US President said he would prefer not to use military action against the nuclear state, but warned "nothing is inevitable".

He said: "Each new day equipment is delivered, new and beautiful equipment, the best in the world.

"The best anywhere in the world, by far.

"Hopefully, we're not going to have to use it on North Korea.

"If we do use it on North Korea, it will be a very sad day for North Korea."

What happens now with North Korea?

According to Sky News Asia Correspondent, Katie Stallard, it is clear what the intentions of the "Rocket Man" are, but less clear are his motives:

She said: "At this stage we cannot know Kim's true intentions - what we do know is that despite the condemnation and the international sanctions, he shows absolutely no sign of voluntarily abandoning his nuclear or missile programmes."