The Reagan administration's decision to ban the import of South African kruggerrands caused a flurry of new demand for the gold coins yesterday as speculators began buying them up in anticipation of future scarcity, according to a leading Washington area dealer in the coins.

But the long-term impact of the president's decision is expected to be minimal, several experts agreed. Although new kruggerands will no longer be allowed into the country, there are still an estimated 15 million to 20 million of the gold coins in circulation in this country and U.S. investors will still be able to buy and sell them.

"As long as its legal, there are hundreds of thousands of people who are going to want them," said Otto Ruesch, president of the Washington precious-metals and foreign-currency firm Ruesch International. "When people want to invest in gold, they couldn't care less whether they are from South Africa or the Soviet Union . . . or Bolivia."

Ruesch said his own company's krugerrand sales began increasing Tuesday afternoon when word first broke that Reagan had decided to impose the ban. It continued throughout the day yesterday, with between 50 percent and 70 percent of his gold coin purchasers requesting krugerrands rather than the Canadian Maple Leaf or other coins -- compared with only about a 30 percent demand for krugerrands before the decision.

Reagan had announced Sept. 9, as part of a broader package of sanctions against South Africa, that he would consult with other signators to the General Agreement on Tariffs and Trade to determine if they had any objections under the treaty to a unilateral U.S. ban on the krugerrand.

A State Department spokesman said yesterday that U.S. officials had consulted with "all our major trading partners" since then. "None objected to what we are doing," the spokesman said. "All agreed it could be done."

As a result, Reagan announced Tuesday that all krugerrand imports would be banned, effective Oct. 11, "in recognition of the fact that the krugerrand is perceived in the Congress as an important symbol of apartheid."

The krugerrand has been marketed in the U.S. by Intergold, a New York-based trading arm of the South African Chamber of Mines. It has long been the most popular of all gold coins among investors and last year was the largest single U.S. import from South Africa with $484 million in sales.

But imports dropped dramatically this year amid widespread protests over South African racial policies. Only $87.8 million worth of the gold coin was sold here during the first six months of this year. In addition, some krugerrand dealers found themselves the target of political protests and at least one leading trader -- the precious metal firm of Deak-Perera Inc. -- announced in August that it was suspending its sales of the coin in light of congressional moves to cut off its import.

A spokesman for the South African Embassy yesterday expressed his government's "disappointment" in the president's decision and said it would primarily hurt the approximately 500,000 blacks -- including a large percentage from neighboring countries, such as Mozambique or Lesotho -- who work in South African gold mines.

"Sure, we are concerned," said Peter Swanepoel, an embassy spokesman. "In the end, it will have an effect on the South African economy."