Pierre Cardin is about to begin a vigorous courtship of the Soviet Union's fashion-starved youth.

The French couturier today concluded a three-day trip here with a tentative agreement to sell the Soviet Union a twice-yearly collection of 100 styles for clothes to be produced in Soviet factories.

It will be the first time a western designer puts his imprint on Soviet clothing, and another sign that the new leadership here is interested in trying to please the Soviet consumer.

At a press conference, Cardin heralded the new era with glowing praise for Raisa Gorbachev, the wife of Soviet leader Mikhail Gorbachev, whom he met in Paris last October. At that time, she visited Cardin's warehouse, where models presented 60 of his designs for her.

"The Soviet people now have an ideal image in the first lady," said Cardin. "She is very beautiful, very elegant, and she dresses divinely."

Cardin, who wore a striped blue shirt with a rounded white collar and had a purple scarf in his coat pocket, described his venture as being in part an advertisement for France. "Fashion," he said, "is practically French."

The final agreement between Cardin and the Ministry of Light Industry is still to come, and a number of details have yet to be worked out, including quantity, pricing, distribution and quality control. Cardin would not disclose the terms of the agreement.

Even if all goes smoothly, Cardin said it would be at least a year before the first Cardin dress comes off a Soviet assembly line.

But Cardin is optimistic, saying today he hoped that in two years, 5 million Soviets will be wearing his clothes. Further down the road, he expects to open a store in Moscow's Olympic village where the Cardin goods would be sold.

"Soviet youth is superb. There are 100 million people here between the ages of 16 and 25," he said. "There is a huge commercial potential."

Cardin said the clothes would be made at 32 factories around the Soviet Union, using local materials and existing equipment. The quality of the product would be maintained by teams of observers who would come from France to help supervise production, he said.

Western designer fashions now are just a dream for most Soviets, who make do with locally made clothes that are often of shoddy quality. Occasionally, a delivery of Finnish boots or Japanese raincoats will make it into Moscow stores, but as soon as they arrive, a line forms and the shelves are cleaned out.

There are stores with a small selection of western clothes but they are barred to Soviet citizens, except those with hard currency such as dollars, pounds or francs. Otherwise, fashionable imports are brought into the country singly, bought by Soviets who go abroad, and sometimes make their way into the secondhand shops.

Cardin today said he had long hoped to enter the Soviet market, which will be the 98th country to sell his brand-name fashions. Fashion and clothes, he said, are important elements in any economy. "No one expected it," he said, "but Russia understands the importance of fashion."