Former U.N. secretary general Kurt Waldheim has written a detailed denial of charges that he took part in atrocities against Yugoslav partisans and directed interrogation of prisoners during his service as a German Army officer in World War II, his son said yesterday.

The son, Gerhard Waldheim, gave The Washington Post a 13-page memo in which his father tacitly admitted that in his memoirs he had concealed the fact that he spent three years as a German officer in the Balkans.

He now acknowledges that as an Austrian national, he served with the German Army in Yugoslavia and Greece from April, 1942 until the end of the war in 1945. But he insisted that all of his duties in that period were as a noncombatant staff officer and principally involved being a German-Italian interpreter.

In his 1977 book "The Challenge of Peace," Waldheim said that after being wounded on the Russian front in 1941, he was medically discharged from the Army and spent the rest of the war years in Vienna working on his doctorate in law. He later entered the Austrian diplomatic service and was his country's foreign minister before going to the United Nations. He currently is a candidate for president of Austria in elections to be held May 4.

In the memo, Waldheim seeks to establish that he was stationed elsewhere when the Army group to which he was attached staged massacres and burned Yugoslav villages in 1942 and 1944. The elder Waldheim further asserted that other allegations against him are due to misunderstandings about the titles and duties ascribed to him in German Army records.

Gerhard Waldheim said the memorandum is being sent to the current U.N. Secretary General, Javier Perez de Cuellar, and to his father's American publisher, James Adler of Bethesda.

The son said he had done most of the research for the memorandum after urging his father to make a full disclosure of his wartime activities. He described it as his family's first attempt to answer in a comprehensive way the accusations that have raised a cloud over Kurt Waldheim's reputation since last month when the World Jewish Congress made public a number of documents about his wartime record.

The United Nations today will allow representatives of the Israeli and Austrian governments to examine and make photocopies of the hitherto secret file on Waldheim in the world organization's New York archive.

The most important document there is believed to be a 1948 Yugoslav War Crimes Commission report. The Yugoslav government has not disclosed its contents, but a Belgrade newspaper last month published what it said was a facsimile of a 1947 document stating that Waldheim was wanted in connection with "murder, slaughter, shooting of hostages and ravaging of property by burning of settlements."

The detailed rebuttal prepared by Waldheim seems unlikely, by itself, to end the controversy over his war record. Austrian Chancellor Fred Sinowatz, who supports Waldheim's opponent for president, said in Vienna yesterday that he believes Waldheim's credibility has been damaged regardless of what might be disclosed by the U.N. files.

Elan Steinberg, executive director of the World Jewish Congress, said in a telephone interview that he had not seen Waldheim's rebuttal of the documents found by the congress' researchers in various archives. When he was given a paraphrased description of Waldheim's explanations, Steinberg replied:

"Pending a point-by-point refutation of these assertions, let me note that this, the fifth version from the Waldheim camp of what he was doing in the Balkans, is as much palpable nonsense as the previous explanations . . . . The credibility of Dr. Waldheim leaves much to be desired."

Waldheim's memorandum and an oral elaboration provided by his son expanded on arguments he had made previously in various interviews and public statements. They put particular emphasis on three charges prompted by the documents that have been made public:

*That Waldheim was involved in operations conducted in July 1942 by the German Army's Combat Group West Bosnia against partisans in Yugoslavia's Kozara Mountains that reportedly resulted in the killing of 3,500 partisans and the seizing of 8,000 suspected sympathizers.

*That as a staff officer of Army Group E, he was involved during the German Army's retreat to northern Yugoslavia in the burning of villages in the vicinity of Stip and Kocane on Oct. 20, 1944.

*That while serving at Army Group E's high command headquarters at Arsakli near Salonika, Greece, from late 1942 to October 1944, he supervised and participated in the interrogation of prisoners and was in a position in which he had to be aware that this Army group was ordering mass deportations of Greek Jews to death camps.

In replying to the first charge, Waldheim said that after recovering from his wound and being declared unfit for combat duty, he was transferred to the Combat Group West Bosnia as a lieutenant. He contended, however, that this was only a paper assignment for record-keeping purposes and that he was sent almost immediately to be a liaison officer with the Italian infantry division Pusteria, located almost 200 miles away, and was with the Italian forces when the Kozara Mountains massacre occurred.

Waldheim also denied being in the area of the villages burned during the German retreat in 1944. He said that he was among several Army Group E staff officers who were evacuated by airplane to the vicinity of Mitrovica, about 200 miles north of those villages, on Oct. 13, 1944, a week before the settlements were burned.

The document published by the Belgrade newspaper quoted testimony against Waldheim by Johan Mayer, an Austrian clerk who worked in the German military headquarters and who was taken prisoner by the Yugoslavs at the war's end.

Gerhard Waldheim said Austrian newspapers have published reports that Mayer, who died in 1972, later told friends and relatives that he had sought to curry favor with his captors by identifying as war criminals officers from his unit whom he knew to be dead or otherwise beyond Yugoslav reach. The son also characterized Mayer as an unreliable individual who had been convicted five times of crimes in Austria after the war.

Kurt Waldheim also stated categorically that he never participated in any prisoner interrogations at Arsakli or elsewhere. To buttress that claim, he said all interrogations were conducted at lower levels than the command headquarters where he served and that he spoke none of the languages -- Greek, Bulgarian, Macedonian or Serbo-Croatian -- that would have been required for such a job.

In response to allegations that he has some knowledge of Serbo-Croatian, Waldheim said that in his application for the Austrian diplomatic service in 1945, he noted that he had acquired "a few words of Serbo-Croatian," but that it had been a rudimentary knowledge.

He also acknowledged that his signature was on some intelligence documents that deal with interrogations. But, he added, part of his job was to forward massive amounts of paperwork to superior officers and he merely certified them as "correct copies" without examining their contents.

Lastly, Waldheim insisted that he did not know about Jewish deportations from Greece, partly because frequent leaves to pursue his studies and other temporary assignments kept him away from the Salonika area while much of this activity was going on. In addition, he said, reports from operational units under his headquarters unit dealt only with military matters, while those that would have involved Jewish deportations went to another office of the Army group.