President Carter's statements on his nuclear power policy and later clarifications by the White House and State Department have deepened uncertainty over the future of Japan's nuclear energy program.

The Japanese receive all their enriched uranium from the United States, and are negotiating for the right to reprocess that spent fuel, a process that creates deadly plutonium as a byproduct.

In a Washington press conference yesterday, Carter seemed to concede that Japan could open its new $130 million Tokai reprocessing plant if it wished. "We are not trying to impose out will on those nations like Japan, France, Britain and West Germany which already have, or will soon have reprocessing plants in operation," Carter said.

Responding later to a question, he said countries like Japan have "a perfect right to go ahead and continue with their own reprocessing efforts."

Japanese diplomats who sought clarification in Tokyo and Washington were told that current negotiations on the possible use of American uranium in the Tokai reprocessing plant would continue.

Under a 1958 bilateral agreement on cooperation in the peaceful uses of atomic energy, Washington retains veto power over the reprocessing of U.S. supplied fuel.

At first it was not plain what Carter meant," said an official Japanese source. "We asked for clarification and were told President Carter had not prejudged approval of the Tokai plant."

Japanese diplomats were told that basic U.S. policy would be unchanged: The United States will guarantee uranium supplies to Japan, obviating the need to reprocess spent fuel rods.

Once understood, the Carter statement contained no unexpected shocks.It did not, however, dispel concern in government circles over a serious issue with political and national security overtones for Japan.

Although it is entirely in sympathy with Carter's intention to halt the spread of nuclear weapons, the Japanese government is committed to the plutonium technology Carter wishes toshelve indefinitely. Plutonium-burning fast-breeder reactors would complete the nuclear fuel cycle and reduce resource-poor Japan's dependence on imported oil and uranium.

"We can't accept such hard lines on plutonium so we will have to negotiate with Mr. Carter again," said the government source. "We want to open the Tokai plant in July as scheduled."

The Tokai plant, which would become a white elephant if Japan acceded to American wishes, is an embarrasing obstacle to a compromise solution. Premier Takeo Fukuda's government is already under attack by the parliamentary opposition for its nuclear energy policy. Cancelation of the just-completed plant under American pressure would present difficult political problems.

The confusion over Carter's meaning was shared and unwittingy encouraged by Japanese correspondents in Washington. Morning editions of the mass circulation daily Asahi Shimbun reflected the initial optimistic interpretation with the headline U.S. President says West Germany and Japan have the Right to Reprocess." The evening editions, published after correspondents received background briefing from U.S. officials, were markedly downbeat with the head: "We Are Not Optimistic Over Negotiations With the U.S."

Foreign Minister IIchiro Hatoyama told reporters at a press conference he saw "some flexibility" in Carter's stand, but cautioned against optimism.

Japanese officials involved in the dispute were relieved that Carter did not make an outright declaration that U.S. supplied fuels could not be reprocessed as his campaign statements had led them to fear.

"President Carter has obviously recognized the differences in the energy situations of countries such as Japan and West Germany," said Masahiro Kawasaki, a senior official of the Science and Technology Agency.

In grouping Japan with West European nations already reprocessing uranium, Carter has encouraged the Japanese to believe they will not be singled out in a discriminatory fashion to give up their reprocessing program. The Tokyo government is expect to follow up by asking for multinational discussions on the non-proliferation of nuclear weapons and an international agreement on the development of nuclear energy.

Robert Strauss, Carter's special trade reperesentative wound up 2 1/2 days of "exceedingly productive conversations" with Japanese officials and announced that an agreement limiting color television exports to the United States was close. Strauss said the stage was set for a quick settlement and discussions would continue next week, probably in Washington.

A flood of 2.96 million Japanese color televisions into the United States last year triggered complaints by trade unions and domestic manutacturers. Negotiations are aimed at producing agreement on an acceptable level of imports before Carter rules on a U.S. International Trade Commission recommendation that tariffs be raised 20 per cent.

Strauss said the ceiling on Japanese imports was not decided and called press reports of voluntary self-restraint by the Japanese "a bit exaggerated." Sources insist that Japan has made the offer, but the U.S. side is insisting on something firmer, arrived at jointly.