President Carter yesterday authorized the Pentagon to consider upgrading 432,530 undesirable and general discharges given to Vietnam war veterans for desertion, drug abuse and other charges.

The program was described by the Defense Department as one of "forgiveness and compassion" but stopped short of the amnesity advocated by a coalition of national organizations. Unlike President Carter's blanket pardon of draft evaders, each veteran seeking a review of his discharge will have to apply to special government boards within the next six months.

The Pentagon promised to spell out the mechanics of the application and review process within a week.

The review is open to 173.006 Vietnam veterans who received undesirable discharges including 69,170 deserters who did not participate in former President Ford's clemency program, and to 259,524 veterans who received general discharges between Aug. 4, 1964, and March 28, 1973.

Defense Secretary Harold Brown, in announcing the program, said it "will not apply to those who were separated for reasons involving violence, criminal intent or the use of force."

The Pentagon statement added that service people who deserted during the Vietnam era may participate in the new program but must "return military control" for discharge. "Those who deserted from a combat zone are not eligible," the Pentagon said.

Also, the Pentagon said servicemen who deserted and elect to step forward to be discharged under the program may be prosecuted for pending charges other than desertion.

The program does not affect the 1,903 dishonorable and 28,759 bad conduct discharges issued to servicemen after court-martial.

There were five types of discharges issued during the Vietnam War honorable, general under honorable conditions, undesirable, bad conduct and dishonorable. The latter two were part of the penalty after being convicted in a court-martial.

Only veterans with honorable and general discharges are eligible for the GI bill and other government benefits. The new program would upgrade undesirable discharges to general or honorable and general discharges to honorable.

Although a general discharge does not penalize a service person in the eyes of the federal government as far as benefits are concerned, it does carry a stigma that pro-amnesty groups contend keeps veterans from being hired in many cases.

The Rev. Barry W. Lynn, a member of the steering committee on the Naitonal Council for Universal and Unconditional Amnesty, said last night that Carter should have just mailed out honorable discharges to service people with general or undesirable ones.

Lynn said Carter's program represents "a few slices of the loaf" amnesty groups have pressed for but is a "significant" decision because it amounts to the government admitting that "the military discharge system was so bad that they have to come up with something."