BONN, FEB. 15 -- Austrian President Kurt Waldheim today challenged criticisms leveled against him by a commission of historians that studied his World War II record, and he vowed to stay in office to honor what he said were the wishes of voters who elected him.

The Socialist Party, which heads Austria's ruling coalition, criticized the speech as inadequate and said Waldheim would remain "an immense burden" for the country. Chancellor Franz Vranitzky, a Socialist, warned yesterday that he might resign unless the Waldheim affair is cleared up.

In a 10-minute televised address in Vienna tonight, Waldheim said that he may have made "a mistake" by neglecting in the past to discuss in detail his service from 1942 to 1945 as a staff lieutenant with a German Army unit that committed war crimes in the Balkans.

But Waldheim said that he had not carried out "a strategy of concealment" of his past, and that in many cases he could not remember events of more than 40 years ago. The international historians' commission, which issued its report to the government a week ago, criticized Waldheim for repeatedly seeking to cover up his war record.

Responding indirectly to the panel's conclusion that he should have protested against war crimes he was aware of, Waldheim said: "I have great respect for the heroes and martyrs of this period, but, as always in history, they were only a few."

Waldheim challenged the report's accuracy without going into specifics. "Parts of this report do not correspond to the facts, but are built on suppositions and hypotheses. Therefore the conclusions drawn cannot be upheld," he said.

Waldheim, a former secretary general of the United Nations, rebuffed increasing domestic pressure to resign. Elected with nearly 54 percent of the vote in 1986, he is scheduled to serve until 1992.

"A head of state should not yield to slander, hateful demonstrations and sweeping judgments," he said of the mounting attacks against him. "The belief in our fatherland is at stake," he said, and resignation would throw into question "the whole significance of democratic decisions."

"My dear countrymen," he said, "you can trust me as you trusted two years ago when you elected me."

Vranitzky dropped a political bombshell by saying yesterday that the Waldheim case was consuming up to 60 percent of his time, and that he may have to step down unless the affair is resolved so that it no longer prevents him from governing effectively.

Vranitzky heads the government, while Waldheim holds the largely ceremonial post of chief of state.

Vranitzky has made it clear that he would like Waldheim to resign. His coalition cannot press the issue, however, because it includes the conservative People's Party, whose leadership still backs Waldheim.

Senior Socialist Party official Heinrich Keller said tonight that the party was "very disappointed" with Waldheim's speech because it addressed "the issue of the past, and not the future." Waldheim would continue to be "an immense burden" for Austria, Keller said.

Another senior Austrian Socialist Party official said Waldheim should either resign or "take on a considerable part of explaining his personal circumstances himself."

But Waldheim had not been expected to do either this evening, and Vranitzky is not likely to step down in the immediate future, the official said in a telephone interview.

A West German television poll last week found 66 percent of Austrians questioned said Waldheim should remain in office. Socialist officials and western diplomats said that the survey was made before the historians' conclusions had had time to sink in.

People's Party leader Alois Mock, who also is vice chancellor and foreign minister, continued to defend Waldheim in a newspaper interview today. But he indicated he is prepared to discuss a "new definition" of the president's duties. He did not give details.

If Vranitzky resigned, it would trigger a major political crisis that would likely result either in new parliamentary elections or formation of a conservative-led government excluding the Socialists.

Relations between Waldheim and Vranitzky worsened sharply last week when the president threatened to dissolve the government unless it rejected the historians' report. The report was accepted at Vranitzky's insistence.

In a statement clearly aimed at Vranitzky, Waldheim said, "I appeal to all Austrians, particularly to all those in our homeland who are in politically responsible positions, not to pour oil on the fire, and to put the interests of the state before party political interests."

Special correspondent Peter Hoffer in Vienna contributed to this article.