Yevgeny Velikhov, Russia's delegate to the international council that is to arbitrate between two the bids, said that Russian and Japanese officials meeting in Moscow had "decided to make the final decision at the next meeting of the ITER Council in Vienna in February," the ITAR-TASS news agency said.
Japanese Education, Culture, Sport, Science and Technology Minister Takeo Kawamura held close-door talks with Atomic Energy Minister Alexander Rumyantsev on Thursday in a bid to secure Moscow's backing in the contest to build the first reactor to generate nuclear energy in the same way that the sun does.
Nuclear fusion involves bringing atomic particles together rather than splitting them apart.
It is regarded as clean and safe, avoiding many of the pollution problems involved in fission, and could theoretically generate energy using sea-water as fuel, but so far scientists have been unable to design a commercially-viable fusion reactor.
The site for the first such reactor was due to have been announced in Washington last month at a meeting between participants in the project -- the European Union, the United States, China, Japan, South Korea and Russia.
After the failure to reach a consensus, the decision was delayed and is expected to be made in mid-February.
The choice of the site must be made by consensus rather than by a simple majority, partly because all parties will be required to fund the project.
After Kawamura's talks with Rumyantsev, Velikhov noted that nothing had changed: "Russia and China are inclined to back France, while Seoul and Washington have supported Japan until the last moment," he told ITAR-TASS.
Kawamura however said the Japan had still not given up hope of gaining Russia's backing.
A Russian expert, Valentin Smirnov of the Kurchatov Research Centre for Nuclear Synthesis, noted that the Japanese-proposed site at Rokkasho, in the norther Aomori prefecture, was "not inferior" to a rival French site at Caradache, near the southern port of Marseille.
However France has an edge because the initial expense of running the fusion reactor in Japan would be much higher than in France, he said.
A Russian source close to the talks said Moscow had proposed a compromise arrangement under which the reactor would be built at Cadarache while the computer center to control the experimental work could be set up at Rokkasho.
The ITER Council might consider the compromise, the source said.
The project to build the first fusion reactor is expected to cost more than five billion dollars.
"Some two billion dollars have already been used on preparatory work. The country which gains the right to operate the reactor, should cover 42 percent of the cost of the project," ITAR-TASS quoted Velikhov as saying.
Kawarmura, heading a 10-strong Japanese delegation, held talks Wednesday with his South Korean counterpart Oh Myung and was due Friday to fly to Beijing for talks with China's science and technology minister Xu Guanhua.