South Africa, barred from using American-enriched uranium in nuclear power plants because it rejects international safeguards, has come up with enough enriched fuel to launch its first plant on schedule next June.

Framatome, one of the three French companies in the giant consortium that is building South Africa's two 1,000-megawatt power plants near Cape Town, is believed to have received in France a shipment of South African-owned enriched uranium that it has contracted to load into fuel rods to be sent here.

Since the company is one-third government owned, Framatome needs French government approval to export the fuel-packed rods to South Africa. But in a statement that is likely to provoke a negative response from the Reagan administration, a French Foreign Ministry spokesman said today in Paris that the government of President Francois Mitterrand has no plans to hold up fulfillment of what he described as a "normal contract."

An informed U.S. official reached by telephone in Washington said the United States had received no advance notification of the French decision and charged that the re-export would mean that "the Mitterrand government has undercut Reagan administration policy" of using the fuel as leverage in ongoing safeguards talks between Washington and Pretoria, and would make the administration look "foolish."

The administration is likely to be particularly irritated because of France's criticism of U.S. policy on other issues in South Africa as being too sympathetic with the white-minority government.

The French position, as stated by the spokesman, is that Mitterrand has committed his government to honor all contracts signed by the previous French administration and that "the U.S. authorities know very well the terms of the South African contract, and what it obliges us to do."

An even more important issue, according to the U.S. official, is where South Africa obtained the fuel in the first place. He said there is no indication that it came from France itself, which is one of five international suppliers of enriched uranium, along with the United States, China, the Soviet Union and a British-Dutch-West German group called Urenco.

While stressing that the administration has no confirmation, he said that one likely source was China. Earlier press reports have speculated that China has been shipping weapons-grade uranium to South Africa. The official said a possible route from China to France was through uranium "launderers" in Switzerland, and then through another country such as West Germany or Belgium.

A spokesman for the French government Atomic Energy Commission said that while the agency is charged with monitoring entry and exit of enriched uranium, it had received no orders to treat the South African uranium differently from any other. Framatome company spokesman Jacques Gossens in Paris said in a telephone interview that it was not France's business where South Africa obtained the enriched uranium.

The question of whether South Africa had obtained enriched uranium to fire up a plant, despite U.S. denial of the fuel, was initially raised last week, when Framatome announced in Paris that the initial fuel loading of the first station would proceed on schedule next June.

In telephone interviews on Monday and Tuesday, Framatome spokesman Gossens confirmed that his company had been given low-enriched (3 percent) uranium hexafluoride from South Africa's Electricity Supply Commission (Escom), the state agency that owns and will run the plants. Framatome is now preparing to transform it into fuel elements for the first plant, Gossens said.

When asked the origin of the material, he said he did not know.

Questioned again today, Gossens said he had been misunderstood and that he had been informed by Escom that the fuel had been obtained and would be delivered to Framatome "any time now."

ESCOM chairman Jan Smith said here that "until things are finalized" he could say nothing. He reminded his caller that in an interview in July he had said that although the South Africans still hoped to get the fuel from the United States, they were looking at "alternate ways and means" of getting it.

The supply of U.S.-enriched fuel for the two plants at Koeberg was a key bargaining lever for Washington in its efforts to get South Africa to accept full-scope safeguards on its atomic energy facilities. Without the fuel, the scheduled launching of the plants was threatened with delay at a cost above $1 million a day, according to South African estimates.

"You could say they were able to get the fuel for Koeberg without complying with safeguards," a senior State Department official said. "But that does not solve their main problem with us, which is their contract under which they have a big obligation."

Under a multimillion-dollar contract South Africa has with the U.S. Department of Energy that extends into the 1990s, Escom is obliged to deliver raw uranium to the United States for enrichment at regular intervals.

Originally, this uranium was to be used in the Koeberg plants. But when the Ford administration began to suspect that South Africa was working on a nuclear weapon, it notified Pretoria that it would not be able to get the required export permits for the enriched material until it signed the Nuclear Nonproliferation Treaty.

Then, in 1978, the U.S. Congress passed a law requiring any country receiving U.S.-enriched uranium to agree to full-scope safeguards of the International Atomic Energy Agency on its entire atomic energy program. South Africa refuses to do this, saying it fears that what it describes as a unique method of enrichment would be compromised.

Some observers have suggested that South Africa enriched the fuel itself in its small pilot plant set up in 1975, but others say this is unlikely.

Obviously it has the capacity to do so because last April it announced that it had enriched a limited amount of uranium. But it may have lacked the time to enrich the relatively large amount required for Koeberg I's initial loading.

Despite Mitterrand's anti-South Africa position, France has much to lose financially if the Koeberg deal does not come to fruition.