The White House has told the National Aeronautics and Space Administration it may have to cut as much as $760 million from its fiscal 1981 budget as parts of the new effort to reduce inflation.

That $760 million amounts to more than 14 percent of the civilian space budget for 1981. A reduction that large would require changes in all NASA's large programs.

"At $760 million," one highly placed NASA source said yesterday, "you touch everything, including the space shuttle."

The $760 million is only a target subject to negotiation between NASA and the White House Office of Management and Budget. NASA Administrator Robert A. Frosch already has replied to OMB about the target, contesting its size.

A cut of $760 million in the $5.7 billion NASA budget would almost surely mean a stretchout in the Galileo program to orbit the planet Jupiter in 1985, and in missions to fly around the north and south poles of the sun in 1984 and to orbit the Large Space Telescope around the Earth in 1983. A cut that size could even mean the end of one of the three projects, whose combined cost in fiscal 1981 comes to $265 million.

The biggest impact of a budget cut of $760 million would be on the space shuttle, whose maiden flight is scheduled for November of this year but is not expected before the first quarter of 1981. A sizable cut in the fiscal 1981 budget would mean new delays in the whole shuttle program.

NASA is asking Congress for more than $2.7 billion for the shuttle in fiscal 1981, including $1.8 billion to design, develop and test its engines and airframe and to continue production of the first three shuttle spacecraft.

The fiscal 1981 budget also includes a request of $809 million to begin shuttle space flight operations, assuming the shuttle begins to fly early next year. Delaying the first shuttle flight would reduce the request for flight operations.