Story highlights That would be an acceleration of two years from previous estimates

The official clarified that while the DPRK can currently get a missile "off the ground," there are still a lot of undetermined variables

Washington (CNN) The US believes that North Korea will be able to launch a reliable nuclear-capable intercontinental ballistic missile (ICBM) by early 2018, a US official familiar with the latest intelligence assessment confirmed to CNN Wednesday.

That would be an acceleration of two years from previous estimates that put Pyongyang three to five years from fully developing long-range missile capabilities.

The official clarified to CNN that while North Korea can currently get a missile "off the ground," there are still a lot of undetermined variables about guidance, re-entry and the ability to hit a specific target.

The ongoing assessment from the US intelligence community in recent months has been that North Korea has accelerated its intercontinental range ballistic missile program.

On Tuesday, a spokesperson for the Defense Intelligence Agency declined to comment directly on a report from The Washington Post that the agency's latest assessment concludes Pyongyang will have a nuclear-capable intercontinental ballistic missile as early as next year but admitted that Pyongyang's missile capabilities are progressing.

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