Aliens will crush humans in a terrifying war of the worlds and could "crack this planet open like a nut", according to a UFO expert.

Nick Pope, who investigated UFOs for the Ministry of Defence, says humans are toast if ETs invade because their weapons will probably be billions of years ahead of ours.

He says sci-fi flicks where humans vanquish hordes of invading little green men are unrealistic, as their weapons would be so advanced they’d seem like "magic".

US spooks published a bombshell report on UFOs earlier this month.

It concluded that 143 unidentified aerial phenomena sightings by US military pilots since 2004 remained unexplained, fuelling further fears of an alien invasion.

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