Japan could import as much as 400,000 metric tons of rice this year from the United States, analysts say, after Japan's food agency signaled last weekend that a one-time emergency rice import program will go into effect in 1993-94.

While officials told reporters that total rice imports this year might equal several hundred thousand tons, analysts believe it could be much higher - perhaps as much as 1 million to 1.5 million tons - given this cold, wet summer and years of weak harvests that have depleted reserves.Toshiharu Nisiguchi, analyst with the Tokyo-based Rice Databank, believes Japan will import between 200,000 and 400,000 tons of medium-length staple rice from the United States and about 300,000 tons of the staple variety from Australia.In addition, it will import about 150,000 tons for processed food from Thailand. Mr. Nisiguchi also believes there will be several hundred additional tons of lower-grade rice brought in from other Asian countries including China, Vietnam and perhaps South Korea. The latter, however, has also suffered some of the same weather as Japan this year.Tomoko Asano, representing the Rice Growers Cooperative Ltd. based in New South Wales, Australia, said Australia has up to 200,000 tons of Japonica table rice available immediately and up to 300,000 tons it could supply by next June.

Some of the lower-grade rice, meanwhile, destined for processed foods is already being shipped, Mr. Nisiguchi said. Shipments of premium rice could begin within a matter of months.

Japan usually produces about 10.3 million tons of rice annually and consumes about 10 million tons before storing the rest. But its surplus has been depleted to about 400,000 tons. And this year's poor harvest - caused by cool temperatures, record rains, fungus and typhoons - is expected to produce yields at 80 percent of normal.

These will be Japan's first large-scale import program since 1984, when Japan "borrowed" 150,000 tons from neighboring South Korea. U.S. rice groups have called on Japan to import American rice if it imports anything.

Chalmers Johnson, a professor emeritus at University of California at Santa Barbara, said in a telephone interview that the United States should be pushing Japan much harder on this issue.

"I can't for the life of me understand why there hasn't been a Section 301 (trade action) suit years ago," he said. "It's American law, and Americans expect it to be followed."

Section 301 of U.S. trade law allows the United States to take retaliatory action if it finds it is being discriminated against.

But other analysts said U.S. negotiators may have concluded there is relatively little to gain in dollar terms by pushing Japan on the rice issue.

Given Japan's political sensitivity, it may be advantageous to lower the temperature in this area in return for concessions elsewhere, said Robert Bullock, a doctoral candidate at the University of California at Berkeley doing his dissertation on the Japanese rice issue.

Mr. Bullock added that the bureaucracy would maintain substantial control over imports even after de facto liberalization through "administrative guidance" and its hold over importers.