It was near the end of a speech he was giving at a factory in Dnepropetrovsk late last June when Soviet leader Mikhail Gorbachev seemed to erupt, accusing the Reagan White House of nothing less than girding for a "nuclear strike against our country with impunity."

If the situation continued -- if Washington pursued its Strategic Defense Initiative and the U.S. negotiators in Geneva kept on dragging their feet -- Gorbachev warned, the Kremlin would be forced to "reappraise the whole situation."

The next day word leaked out to The Washington Post in Moscow that the new Soviet leader had agreed to a summit meeting with President Reagan in Geneva 4 1/2 months later.

Gorbachev's flash of what some Russians call his "iron teeth" to Soviet factory workers one day, and the less confrontational image of a summit-bound superpower leader that he showed the outside world the next, demonstrate the mix of domestic and international aspirations that have driven him to become the first Soviet leader in 6 1/2 years to meet face to face with a U.S. president.

At home, Gorbachev has shown a rock-hard resolve to use the summit to stop the Reagan administration from disrupting Soviet-American military parity with its SDI program for research into a space-based antimissile system.

Abroad, he has cast the meeting with Reagan more as a forum to ease international tensions.

In the end, the Kremlin leader's overriding mission in Geneva, as best a foreign reporter in the Soviet capital can ascertain it, is the same in the Soviet Union and the world over: to demonstrate that the ruler of 274 million Soviet people is an actor on the world stage and a match for his American counterpart as a global leader.

Gorbachev showed his sense of mission to prove the point particularly to the other superpower in a comment to U.S. senators at the Kremlin in September. "Sometimes I wonder if the American side knows who it is dealing with," he said.

Although the 54-year-old Gorbachev, in office slightly more than 250 days, has set his sights on the year 2000 and begun to reach for domestic economic and international goals at least as distant, failure at the summit could turn his aspirations into a wobbly house of cards.

Success at the summit, however, is probably the key link missing in his ongoing consolidation of power in the Soviet leadership. Although, given the Soviet system, there is little doubt that next February's Communist Party Congress will approve the controversial measures Gorbachev has pushed through since coming to power, a summit in which he succeeds in holding his own against the U.S. president would put him in an even stronger position to press such measures. They include a shake-up of senior Kremlin officials, the appointment of four new Politburo members, the selection of a new foreign minister, a new draft of the 1961 party program and a new five-year plan. Abroad, too, the ability to forge a binding arms agreement with the United States would provide Gorbachev with a distinction that has eluded his recent predecessors.

The inexperienced Gorbachev's insistence on drawing swords with Reagan over the SDI may stretch his considerable talents as a forceful communicator and negotiator to their limits.

Gorbachev and other Soviet officials have posed the need to stop the SDI as their reason for participating in the summit. As Radimir Bogdanov, deputy i leader projected a certain flexibility to French officials. More recently, in granting Soviet dissident Yelena Bonner a visa to go to the West for medical treatment, he showed a willingness to improve the summit atmosphere.

But in preparations for the summit, Gorbachev has struck U.S. visitors as an aggressive conversation partner. After a three-hour meeting in September, U.S. senators described him as a "strong-willed," "hard driving," "skillful" debater.

Gorbachev "seems to have his arguments on the U.S. unemployment problem and economic issues all ready," said a U.S. official who has observed him in action, "and to look for places to jump in with them."

Western analysts here consider the different images part of Gorbachev's campaign against Reagan for the title of "great communicator" in the eyes of the world. He is keenly aware that the Soviet Union lost face under his three ailing predecessors, a senior western diplomat observed, and anxious to make up for the time lost in the six years since the last U.S.-Soviet summit.

The Kremlin's all-out effort to block the SDI suggests to analysts here that the vast research program threatens Gorbachev's domestic economic and military plans.

Soviet officials have said in interviews that "negative signals" on the chances of a U.S.-Soviet compromise on the SDI during the summit will probably force the Kremlin to an early decision on whether to counter with its own stepped-up space-strike weapons program, or to pursue a less costly buildup of offensive weapons. In either case, the ensuing increase in weaponry would increase the Soviet defense budget, already an estimated 13 to 14 percent of the gross national product.

Soviet officials couple the public warning that the Kremlin will match the SDI program with private intimations that Washington's inflexibility on it will force Moscow into a defense showdown, including a buildup in high-technology hardware and the return of Marshal Nikolai Ogarkov, perhaps as defense minister. Ogarkov was ousted late last year as chief of staff of the Soviet armed forces, perhaps in a dispute over the need for high-tech modernization of Soviet conventional weapons, which he favored.

Such drastic steps would strain the Soviet civilian economy at the expense of the defense budget and at least brake the pace of Gorbachev's overhaul of the country's moribund industries, if not derail it altogether. Gorbachev has already suggested that the country's budget for industrial modernization be increased from one-third to one-half of total capital expenditures.

With the approach of the summit, pressure has increased for him to reinvigorate the U.S.S.R.'s industrial money earners, particularly the flagging energy industry, which accounts for two-thirds of Soviet hard-currency earnings. Since Gorbachev came to power in March, dwindling oil production and falling rates of income from abroad have threatened to further reduce growth in the country's national income, already less than half the 7 percent rate of the 1960s.

Gorbachev apparently believes that fulfilling his economic goals will require a superpower arms accord. After discussing his domestic economic plans in an interview with Time magazine, he asked the U.S. editors to "ponder . . . what are the external conditions that we need to be able to fulfill those domestic plans?"

So far, Gorbachev has skirted the pertinent question of how he will find the funds needed for new industrial investments to achieve the doubling of industrial output and availability of consumer goods the party has promised by the year 2000.

But even if negative summit results lead him away from that prospect in the short run, they are unlikely to discourage him from his plans altogether. In 2000, the target date for many of his goals, Gorbachev will be 69, younger than Reagan is now. And, if he keeps pace with Leonid Brezhnev's record, he will have five summits with three American presidents under his belt.