Nasa chief Charles Bolden has said the best defence against asteroids is... prayer.

The remark was made at the US House of Representatives Science Committee on Wednesday.

Bolden was discussing Nasa's ability to protect Earth from deadly asteroids - which currently is essentially non-existent.

"From the information we have, we don't know of an asteroid that will threaten the population of the United States," Bolden said, according to Reuters.

"But if it's coming in three weeks, pray. The reason I can't do anything in the next three weeks is because for decades we have put it off."

Nasa is currently tracking about 95% of the asteroids which are hurtling in the sky near our planet and are larger than about a kilometre.

But smaller asteroids can still cause devastation, as shown in Chelyabinsk, Russia, last month where shockwaves generated by an 18-metre meteorite caused more than 1,000 injuries.

And just 10% of the so-called "city-killer" asteroids larger than 165 feet wide have been found so far.

About one of those objects hits the planet every 1,000 years.

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  • Police dash cam of Meteor over Edmonton, Canada

    Meteor falling from the sky in Edmonton, Canada. Filmed about 5:30pm Thursday November 20th 2008.

  • Police dash cam of Meteor over Edmonton, Canada

    Police dash cam of Meteor over Edmonton, Canada. Filmed about 5:30pm Thursday November 20th 2008

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  • Meteor over Netherlands, pictures from Groningen, October 13, 2009. Photographer Robert Mikaelyan

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  • April 2010 Meteor Fireball over Northern Iowa

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