The Jammu-Srinagar National Road, about 270 km long, is the only all-weather road connecting the rest of the country.
The landslide occurred near the town of Ramsoo in Ramban, officials said.
No vehicles passed when the landslide occurred, they said.
 "The agency concerned (a) pressed his men and his machines (in use) and efforts are continuing to restore traffic (traffic) on the highway," said the PTI, Superintendent of Police (National Highway). .
He said that it would take at least five hours to clear the road.
It was closed for several hours due to snowfall in the Peer Ki Gali area on Friday night.
Snow was cleared and blocked vehicles were allowed to move to their destination, officials said, adding that traffic was flowing when the latest reports were received.