President Reagan has approved a new national space policy that calls for an ambitious plan aimed at developing a base on the moon and manned flights to Mars, White House sources said yesterday.

Confirming a report to be published next week in Aviation Week & Space Technology magazine, officials said Reagan approved the policy early this month. The proposal will be contained in a legislative package to be submitted to Congress after the State of the Union address.

The National Aeronautics and Space Administration would not comment on the magazine report. The policy statement reflects many of the proposals made on Capitol Hill over the past two years and shares key recommendations with a recent report on the future of the country's space program by former astronaut Sally Ride.

"Although I cannot verify the accuracy of this report, it is just what the nation needs," said Rep. Bill Nelson (D-Fla.), who chairs a key subcommittee of the House Committee on Science, Space and Technology. "This is the bold new approach to planetary travel and to exploring other planets that our space program must have."

The Reagan administration has been attacked for what its critics have called a failure to act decisively on a long-term policy to ensure the nation's continued eminence in space in the aftermath of the space shuttle Challenger disaster in 1986.

Support from Congress and in the administration for space programs has vacillated in the face of severe budgetary constraints. Athough Reagan has emphasized the importance of constructing an orbiting space station in the 1990s, the proposal has been endangered by budget cuts.

As an initial part of the new policy, the White House has proposed giving NASA $100 million in planning funds to begin a program for the development of new "Pathfinder" technologies, Aviation Week reported, that would be the first step toward giving the United States the ability to return to the moon by the end of the century and to begin flights to Mars early in the 21st century.

As part of the proposal, NASA has been instructed to identify potential cooperative projects that could be raised by Reagan when he meets with Soviet leader Mikhail Gorbachev during a summit planned for this summer in Moscow.

The pursuit of an unmanned Mars flight that would return to earth samples of the planet's surface is one possibility for a joint mission, Aviation Week reported. Before any manned flight to Mars is undertaken both the United States and the Soviets have said that it would be necessary first to send an unmanned test flight.

Aviation Week reported that total funding for the new project would exceed $1 billion and that the policy was unanimously approved by the Senior Interagency Group for Space in late December.

Unlike the Apollo project that put men on the moon in 1969, there is no deadline for returning to the moon or reaching Mars, and it is not clear what level of support the administration will receive from Congress.

In addition, funding of the program will require political support as well as a constant influx of new money for years.

"I think a program with vision will get the support of Congress and of the American people," Nelson said. "We have been waiting for the leadership we need to get it off the ground."

According to the documents obtained by Aviation Week, NASA officials originally had sought $120 million from the administration in the new budget for the project's initial stages, but the Office of Management and Budget approved $100 million.

Among the specific components of the new policy will be:

The launch of an unmanned probe to Mars to return surface samples in the late 1990s.

Development of automatic rendezvous and docking capabilities for mission to the moon and Mars.

The development of new rocket systems to sustain astronauts on lunar and Martian missions. Advanced rocket technology that reduces the amount of fuel -- and weight -- will be needed.

Choosing to return first to the moon and slowly setting sights on Mars was recommended by Ride last August in a report on the future of the U.S. space program.

"Settling Mars should be our eventual goal, but it should not be our first goal," she wrote. Instead, she recommended a selective strategy of growth beginning with a new moon program.