The Pentagon has said that North Korea will be able to field a nuclear-capable, intercontinental ballistic missile (ICBM) as soon as 2018.

The new timeline, coming from the Defence Intelligence Agency, is two years earlier than previous estimates.

The Washington Post has reported the new date is based on recent advancements observed during Pyongyang's latest test of missiles that could reach North America, specifically Alaska or Hawaii.

The launch, which took place the week of 4 July, of the Hwasong-14 was dubbed a "shining success" on North Korean state television.

North Korea "appeared to master key technologies needed to loft a warhead toward targets thousands of miles away," according to the newspaper.

North Korean leader Kim Jong-un could have a “reliable, nuclear-capable ICBM” in production in the next few months, according to people familiar with the confidential assessment.

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

Despite the rapid progression from prototype to production, intelligence officials have said that "rentry" is still an issue for a nuclear-capable ICBM, meaning a warhead could travel through the atmosphere without suffering any damage.

Tests are expected to take place in the next few days - perhaps on 27 July, a national holiday in North Korea to mark the end of the Korean War - and will be watched closely to monitor if the isolated nation has in fact developed the "reentry" technology.

Another "milestone" is making a nuclear warhead that is small enough to place on the missiles, however the country has been conducting tests underground on a possible version of it.

The Trump administration have not indicated as yet how this will change the timeline on action taken to stop North Korea's development of a nuclear weapon being used against North America.

Donald Trump has previously criticised the United Nations Security Council for its inaction, but he reportedly discussed the issue with allies at the last G20 and North Atlantic Treaty Organisation (Nato) summits.