Meteor (1979)

After a collision with a comet, a nearly five mile (eight kilometer) wide piece of the asteroid "Orpheus" is heading toward Earth. If it hits, it will cause an incredible catastrophe which will probably extinguish mankind. To stop the meteor, N.A.S.A. wants to use the illegal nuclear weapon satellite "Hercules", but soon discovers that it doesn't have enough firepower. Their only chance to save the world is to join forces with the U.S.S.R., which has also launched such an illegal satellite. But will both governments agree?