The Reagan administration plans to ask Congress next year for permission to sell some land from the country's national forests to help reduce the national debt.

That announcement Tuesday by Agriculture Secretary John R. Block drew criticism from the Sierra Club and the Wilderness Society, which noted that officials previously have said the sales program would not touch parks and forests.

Block said he already has authority to sell some Forest Service land and will start offering 60,133 acres immediately. That acreage includes forest and grassland restoration projects as well as unneeded administrative units and research centers.It also includes certain parcels under 640 acres that the Forest Service can offer to sell to neighboring local governments for public use.

Block said all Forest Service land would be divided into three groups: those parcels to be retained (51 million acres of wilderness, national recreation areas, national monuments and wild and scenic rivers); acreage to be sold (the 60,133 acres), and acreage that will be studied for possible sale (140 million acres).

Eventually, Block said, 15 million to 18 million acres of the third group will be identified and reviewed closely for possible sale. These include scattered holdings in the national forests and grasslands, lands leased by the Forest Service to private users, and areas in national forests with extensive private ownership.

"The weight of this program will be based on what congressional authority we can get," said Vern Lindholm, assistant director for lands. "The idea is to sell those lands which are least efficient for the Forest Service to manage."

Nearly 46,000 of the acres targeted for immediate sale are in so-called land utilization projects created in the early 1930s. USDA acquired "submarginal farmlands" and relocated farmers who had not been able to make a living on them, Lindholm explained. "We have not sold those lands off, but rehabilitated them, kept them and leased them for commercial uses," such as grazing, farming or foresting.

The Forest Service owns no land in Maryland or the District and none of its 1.6 million acres in Virginia has been identified for early sale. More than a third of the acreage that it will try to sell immediately is in California, with large chunks in New York and Georgia.

The proposal may have rough going in Congress, according to some administration officials and environmental groups. Peter Kirby of the Wilderness Society said, "Block's initiative is another step in the administration's campaign to turn over the wealth of the public lands to corporate interests at giveaway prices."

But the Forest Service said that before any parcels of national grasslands or forests are put up for sale, the department will perform an environmental assessment of the potential impact on wildlife, watersheds and recreation.