Japan's crushing houses, which turn all of the country's oilseed imports into meal and edible oil, face extinction or an industrywide reorganization in the next three years.

The cause, say industry sources, is a rising tide of cheaper oilseed- product imports in a political climate increasingly unfavorable to protective tariffs. The United States has exerted strong pressure on Japan to import more food.''It is fairly common knowledge that the ministry (of Agriculture) is going to ease the tariffs on edible oil imports in response to U.S. demands that we open our markets," said one dealer at a leading commodities trading house here.

According to dealers here and in Hong Kong, the recent flood of cheaper soymeal into Japan also is the result of a countertrade deal with China by a major Japan electronics firm seeking a foothold in the Chinese market.

A longer-term threat to the crushing industry is a widely expected increase in cheap foreign edible oil imports if the government eases current tariff restrictions.

''The entire crushing industry could go from 40 separate ownerships to five or six major owners within the next three years," one dealer commented.

Industry sources say crushing companies have been battered by stagnating domestic demand for edible oil and a recent threefold increase in cheap soymeal imports from China. Japan traditionally has imported most of its oilseed from North America.

Soybean dealers said that because most Japanese crushing houses are operating with minimal to negative profits, it is likely that the ministry has warned them of the move before making it public to give them time to prepare.

The Ministry of Agriculture, however, continues publicly to deny that such a plan exists. But most leading trading companies interviewed agreed that tariffs on food oil imports - averaging about 23 percent of the original price - will be cut 30 percent from April 1991.

If the ministry has warned crushers of potential pressure on edible oil prices from an influx of foreign imports, it is a certain sign that the crushing industry will have to reorganize in the next few years, dealers said.

Some predicted that the industry's houses will be forced to fold; move into other, more profitable areas such as sugar and wheat refining; or form joint crushing ventures under new ownership.

Japan's crushing industry depends on a balance in domestic demand for the two products it derives from crushed soybeans - oil and meal.

As one agricultural specialist at the U.S. Embassy explained, the leap in cheap Chinese soymeal imports has upset that balance. Facing a shrinking domestic market for their more expensive soymeal, crushers have begun to shun soybean imports in favor of the oil-rich and more-expensive canola.

Ministry of Agriculture figures illustrate the gradual shift, showing a 12 percent increase in rapeseed or canola imports from 1.5 million metric tons in 1986 to 1.8 million metric tons in 1989, and a corresponding drop in soybean imports to 3.5 million metric tons from 3.9 million metric tons during the same period.

''Crushers didn't want to produce meal for a feed market that already was filled with Chinese soymeal imports," explained the U.S. specialist about the switch to rapeseed.

At the same time, steady declines in domestic oil prices have worsened the situation. Crushing houses, on average operating at 80 percent of capacity in an effort to reduce supply and help prop prices, still are losing between $5 to $10 a barrel on rapeseed oil once transportation and production costs are deducted.