Donald Trump appears to mock Kim Jong-un with 'Rocket Man' reference

Donald Trump appeared to mock North Korean leader Kim Jong-un - referring to him as "Rocket Man".

The US president made the apparent reference in a tweet on Sunday detailing a conversation with his South Korean counterpart.

Trump revealed he had discussed the growing nuclear crisis on the Korean peninsula with president Moon Jae-in during a phone conversation on Saturday.

In a tweet, Trump said he had asked Moon "how Rocket Man is doing" - a barely veiled reference to Kim.

The president also suggested that queues for gas were growing in North Korea as a result of fresh United Nations sanctions imposed on the country.

North Korea fired a rocket over Japan last week. Credit: AP

Trump's comments came a day after Kim vowed North Korea would complete its controversial nuclear weapons ambitions.

The enigmatic leader claimed his country was nearing its goal of military "equilibrium" with the United States - days after firing a missile over Japan.

China, Russia, the UN and US all condemned the launch.

On Sunday, Trump said he had spoken with Moon, saying: "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!"

In recent weeks, US president Donald Trump has repeatedly warned Kim against pursuing the policy - claiming the North would be met with "fire and fury".

The latest missile launch, which travelled 2,300 miles before landing in the Pacific Ocean, was lambasted by the United Nations Security Council as "highly provocative".

Under Kim's leadership, the country has now test flown two intercontinental ballistic missiles and carried out its most powerful nuclear test to date on September 3.

Several rounds of sanctions have been imposed on North Korea. Credit: AP

Meanwhile, Kuwait has decided to expel North Korea's ambassador to the oil-rich country along with four other diplomats.

Kuwait said on Sunday it was taking the "positive steps" to "implement UN resolutions relating to Pyongyang".

The decision will potentially limit North Korea's ability to earn money for its nuclear program from labourers it sends to the Gulf.

North Korea's Embassy in Kuwait City serves as its only diplomatic outpost in the Gulf.

Pyongyang has thousands of laborers working in Kuwait, Oman, Qatar and the United Arab Emirates.