JX Nippon Oil and Energy Corp, Japan’s biggest oil refiner, is not renewing one of its two contracts to purchase Iranian crude oil.

Under that contract, Reuters reports, JX Nippon bought 10 thousand barrels of oil per day from Iran, until it expired in March.

Reuters indicates that three additional Japanese companies will stop buying Iranian crude in April.

The cuts, according to Reuters, mean Japanese imports of Iranian crude have decreased by 15 percent in the past 4 days and that in the past two months Japan has decreased import of Irnaian oil by 28 percent.

Under JX Nippon’s other contract, Japan imports 80 thousand barrels of oil per day from Iran. That contract was renewed in January and will continue as before.

Showa Shell Sekiyu K.K., Japan’s biggest buyer of Iranian oil, has also refrained from renewing its annual contract with Iran, but sources have informed Reuters that the firm will resume importing Iranian crude in April.

Japan has managed to get an exemption from U.S. sanctions against countries that import Iranian oil, convincing Washington that it has significantly cut its oil trade with Iran.

The Japanese government has announced that it will continue to reduce Iranian oil imports by 10 to 20 percent each year.