Former vice president Walter F. Mondale said yesterday that if the United States renounced the first use of nuclear weapons, as several former national security officials urged this week, "it might encourage the Soviet Union" to launch an attack on Western Europe which likely would turn into a nuclear war.

While urging faster development of conventional forces in the NATO countries, Mondale supported some of Secretary of State Alexander M. Haig's arguments against the "no-first-strike" pledge urged by four senior advisers in administrations from John F. Kennedy through Jimmy Carter.

But Mondale, in an interview with Washington Post editors and reporters, was critical of the Reagan administration's general approach to foreign policy and its handling of the Falkland Islands dispute between Great Britain and Argentina.

He said Haig's efforts to defuse the crisis stemming from Argentine military occupation of the South Atlantic islands are "probably the best thing we can do right now."

But he said that the Argentine action showed the futility of administration policies of conciliation of authoritarian governments. And he roundly criticized Jeane J. Kirkpatrick, the U.S. representative to the United Nations, for attending a dinner in her honor at the Argentine embassy on the night the invasion took place.

Mondale said that decision on her part "gave off the worst possible signal" and probably "encouraged the Argentine government" to believe the United States approved the invasion of the Falklands.

He said it was as insensitive as if a senior British diplomat had "gone to dinner at the Iranian embassy the night the U.S. hostages were taken." A State Department spokesman said the event had been scheduled for a long time and the attendance of top U.S. diplomats "was appropriate . . . despite the concern over events in the South Atlantic."

In the wide-ranging interview, Mondale repeated many of the criticisms of administration economic and social policy he is making in speeches around the country as he prepares for a bid for the 1984 Democratic presidential nomination.

He accused President Reagan of playing "a cat and mouse game" from his vacation retreat in Barbados while congressmen of both parties negotiate a budget that will correct what Mondale called "the biggest economic error in American history"--the Reagan budget and tax plan.

"The president is not involved," he said. "He's listening and ducking . . . . That is not negotiation."

Mondale said Democrats would negotiate seriously when the president "comes off his position . . . that you can't cut taxes and you can't cut defense." As long as he remains adamant, Mondale said, "about all that's left is wheeling the wheelchairs back to the nursing homes."

But while criticizing Reagan's stubbornness, the former vice president said he would be "very reluctant" to see the Democrats make any concessions on the Social Security cost-of-living formula, because "the old people in this country are suffering terribly" and the threat of bankruptcy to the Social Security trust fund is "greatly exaggerated."

He said the Falklands dispute illustrated a basic error of Reagan's approach to foreign policy. "I hope we've learned that efforts to abandon one's principles to gain concessions from governments such as the South Africans and Argentines not only deny us our moral authority but in all likelihood deny us the concessions that we think someday we might get."

The lone issue in the long interview on which Mondale gave a degree of support to the current administration was the nuclear deterrent in Europe. He said he had read the article in Foreign Affairs magazine in which McGeorge Bundy, national security adviser to presidents Kennedy and Johnson, Robert S. McNamara, secretary of defense in those same administrations, George F. Kennan, former ambassador to the Soviet Union, and Gerard Smith, former head of strategic arms negotiations, urged the United States to renounce the first use of nuclear weapons in a European war.

Noting that he had long advocated a buildup of conventional NATO forces, Mondale said, "They the authors do not answer what they would do until that day when conventional deterrence is strong enough, and I think that is very important."

"The reality," he said, "is that if war breaks out between the United States and the Soviet Union . . . the likelihood of the use of nuclear weapons is very great . . . . What I'm worried about now is that if we drop the so-called flexible response doctrine, while it's generally believed our conventional deterrent is in doubt, then it might encourage the Soviet Union to believe they could be successful in a conventional attack . . . . And thus, the one thing that will most likely cause the use of nuclear weapons--namely, a U.S-Soviet war--could occur."