Japan has told the United States it will spend more than $1 billion to finance plutonium reprocessing plants in France and Great Britain, thus ending any hope the Japanese will not use plutonium as a nuclear fuel.

The Japanese plan comes as a blow to the Carter administration, which earlier this year asked Japan to forgo any plutonium reprocessing plans for at least two years. In effect, Japan has told the Carter administration it cannot do that because it will need the plutonium to fuel its industry in the years ahead.

"We expressed the view that we hoped they wouldn't do it and they explained to us why they have to do it," said one informed source in the Carter administration. "They explained they have no other way."

A delegation from Japan spent most of the past week in Washington, informing the State Department, the Department of Energy and the Nuclear Regulatory Commission of its plutonium plans. The Japanese government expects to make them public in Tokyo next week.

The Japanese plan to sign long-term contracts for France and Great Britain to take Japan's spent nuclear fuel, extract the plutonium back to Japan.

The Japanese intend to pre-pay for the reprocessing by helping to finance construction of a reprocessing plant at Windscale in Britain and expansion of an existing facility at Le Havre in France.

The British Parliament only last week authorized construction of the Windscale plutonium plant, which is to have a rated capacity of 1,600 tons of spent fuel a year. The French plant at Le Havre now reprocesses 400 tons a year and will be expanded to 1,600 tons.

Japan will pay more than $1 billion to France and Great Britain as its share of construction costs. Japan has chosen to acquire its plutonium from France and Great Britain rather than build its own plant because it is faster to do it that way.

The Japanese move was described by one Carter administration official as the "first crack in the dike," meaning that Japan was the first major country to formally move away from President Carter's policy of forgoing the use of plutonium as a nuclear fuel. Other nations, ranging from Latin American countries such as Brazil to most of Western Europe, are contemplating similar decisions toward a "plutonium economy."

Japan's move raises some delicate questions about how the United States might react. Japan's 15 nuclear plants operate on enriched uranium supplied by the United States. Legally, Japan owns whatever plutonium is built up when the uranium is burned, but under the American agreement the United States has the right to approve or disapprove the extraction and transfer of that plutonium in Japan.

"I doubt very seriously the U.S. would cut the Japanese off from its supply of enriched uranium," one Carter administration source said. "But I don't think we'd make any such commitments on the plutonium."

In addition to the 15 nuclear plants it has, Japan is building 13 more, Japan insists it cannot count on fueling these plants with enriched uranium and thus needs to power them with plutonium.

President Carter has deferred indefinitely U.S. use of plutonium and has asked the rest of the world to follow the example. The way the president delayed the U.S. plutonium decision was to withhold funds for Clinch River fast breeder reactor in Tennessee that would produce plutonium and for the reprocessing plant at Barnwell, S.C., that would extract plutonium from spent fuel.

Like the United States, Japan stores spent fuel in huge "swimming pools" of water located adjacent to the nuclear power plants. The Japanese have told the United States they are running out of storage space for spent fuel, another reason they must have the spent fuel reprocessed.