The U.S. Postal Service, in a move that could create a collector's paradise, yesterday suspended sales of millions of stamps and postcards commemorating the Moscow Summer Olympics.

Postal officials said they believed it was the first time the U.S. government has pulled a stamp off the market since the start of the Civil War.

Postmaster General William F. Bolger said the action was taken because of President Carter's decision to boycott the Summer Games unless Soviet troops were withdrawn from Afghanistan. He said he had ordered all philatelic items dealing with the Olympics withdrawn from sale and all promotional posters removed from the nation's 40,000 post offices.

"We're in effect pulling the stock," a postal official said. He said that anyone who has any of the suspended stamps could still use them in the mails.

Postal officials said, however, that any orders for the commemorative items that were post-marked after yesterday would not be honored.

Postal officials said yesterday that all the stamps and promotional materials that had not been sold before the suspension probably would be destroyed if the United States did not participate in the Summer Olympics.

Affected by the suspension were six commemorative stamps, two commemorative postal cards, a commemorative aerogramme and a commemorative embossed stamped envelope. All the items were issued by the postal service between Sept. 5 and Dec. 10 last year.

According to the Postal Service, 67 million 10-cent postal cards were distributed to post offices along with 47.2 million 31-cent airmail stamps and 187.6 million 15-cent stamps which were sold in blocks of four. With the exception of the 15-cent stamps, which were sold out, postal officials said there were large supplies of the postcards and airmail stamps still unsold as of yesterday.

Other items involved in the suspension were 2.5 million 21-cent international postcards, approximately 4 million aerogrammes and 8.5 million embossed envelopes.

Postal officials yesterday said they would not even try to guess the potential collectors' value of the items now in circulation if the government were to destroy all the unsold suspended items.

Some postal officials acknowledged yesterday that the affected stamps could become collectors' items. As to the value of the stamps, one official said: "That quuestion almost defied an answer. We really have no way of knowing."

Bolger apoligized yesterday for any inconvenience his action may cause stamp dealers and collectors. But, he said, "support of national policy took precedence."

He said that "should there be a change in the situation at some future date we will reassess our position. Until then, the materials commemorating the Summer Olympics will be held in storage."