The Pentagon yesterday began the final chapter in the saga of American soldiers in Southeast Asia. It announced that it will resume reviewing the cases of men listed as dead.

The status reviews had been stayed since the winter of 1973, first as a result of a lawsuit filed by families of MIAs, then by an investigation by a special House committee and a presidential commission.

Both investigations concluded there is "no credible evidence" that any missing Americans are alive in Southeast Asia, said a Pentagon spokesman. He said President Carter gave the go-ahead Friday for resuming the Status reviews.

Lt. Col. Carlos Matthews, a top adviser to the Secretary of Defense on Prisoner of War and MIA matters, held out little hope that the reviews would turn up any live bodies or encouraging evidence about the 712 men now listed as MIAs.

"At this stage of the game, there is no indication anyone is alive," said Matthews. "I think it would be safe to say that most, if not all, of the cases will result in a presumptive finding of death."

For most of the families of the missing men, a finding of death will mean a reduction in the money they receive from the Pentagon each month.

While soldiers are listed as missing in action, said Matthews, they are paid their full salaries, tax-free. In most cases, he said, part of the salary is by pre-arrangement forwarded to their families.

Once men are reclassified as presumptively dead, Matthews said, their families receive a death benefit of six months' pay of $3,000, whichever is greater. They are also eligible for a service insurance policy, usually about $20,000, their accrued pay and leave, burial benefits, Social Security, and veterans' benefits.

The Pentagon announcement evoked an anguished protest from the National League of Families, which represents many of the kin of those whose status is in doubt.

"What they're doing is, instead of continuing to press to solve the whole problem, Carter's going to solve it by declaring everyone dead, trying to sweep it under the rug," said spokeswoman Carol Bates.

Bates charged that Carter broke specific promises to the MIA families by approving the status reviews. She cited election campaign promises not to normalize relations with the Vietnamese, nor to let them into the United Nations, until Vietnam gave the United States all the information it is reasonable to assume it had about the missing men.

While conceding that her charge of broken promises depends on one's analysis of the level of Vietnam's efforts to provide information about the MIAs, Bates charged that "the Vietnamese didn't do one whit" before Carter dropped U.S. opposition to U.N. membership for Vietnam in May.

Pentagon spokesman Matthews said the United States has no choice but to rely on Vietnam for information.The men have been missing four to 12 years, and "that particular climate is very unkind to remains," he said. "Any information we're going to get we'll have to depend on the Vietnamese for."

He said the timing of yesterday's annoncement was predicated on a Pentagon realization that "essentially, there's no reason to withhold the reviews any longer."

He said the total of American military missing in Southeast Asia is 2,505. Of them, 1,113 are known dead, he said; since 1973, the families of about 400 more men have requested that their status be changed to presumptively dead. The rest are still missing, he said.

Matthews said the families of the missing men can take attorneys to the status review hearings. If a man declared presumptively dead is later found alive, he said, he will receive full back pay, plus 10 per cent interest, and be allowed to keep his death benefits.