Alfonsin's approval of of rights report puts him on thin ice with military

Spring has ushered in a new chapter of Argentine history: For the first time, a president of this country has endorsed a detailed report on human rights violations.

President Raul Alfonsin accepted a 50,000-page virulent condemnation of the methods used by the military in the mid-1970s to attack leftists. And in doing so, Mr. Alfonsin may have taken the biggest gamble of his nine-month-old government.

The report, delivered to Alfonsin last Thursday by the National Commission on the Disappearance of Persons, is likely to put the President on shakier footing with the military. The armed forces still say the methods pursued against leftists were necessary to stamp out guerrilla groups and their sympathizers and to save Argentina from revolution. This issue, in fact, is the one item on Argentina's political agenda that unites a military that is otherwise divided because of the Falklands debacle.

''Alfonsin is not just shaking hands with the commission he appointed. He is also backing a political condemnation of the armed forces,'' said one irate officer.

Supporters of human rights groups and left-wing parties outnumbered members of the President's party Thursday night in street rallies mounted in support of the commission's report. The slogans grew more angry as the evening wore on. ''The executioner's block, the executioner's block for the military who betrayed the nation,'' people chanted.

The President's dilemma is what to do next. One step it is known he will take is the establishment of a new ministry specifically charged with protecting human rights and analyzing any further evidence on past violations. His basic course, however, seems to be one of moderation. Upon taking office, he moved quickly to order court martials of the most visible figures of the repression that followed the 1976 military coup, including former President Gen. Jorge Rafael Videla, but he argued strongly against a full purge of the armed forces on the grounds it could prove destabilizing. He has stopped short of publishing a list of an estimated 1,300 military officers allegedly responsible for human rights violations.

And so far he as resisted pressure to turn judgment of cases against the military over to civilian courts.

The rights report describes the military regime of the mid '60s as the ''greatest tragedy'' in Argentine history. It says the armed forces reacted with a terrorism that was ''infinitely worse that that perpetuated by their enemy'' because the military exploited the state machinery to kidnap, torture, and assassinate not just left-wing terrorists, but anyone regarded as a political dissident. It says the military ran more than 300 secret detention camps and describes forced abduction, torture, and ''disappearance'' of more than 8,960 Argentines.