Japan announced a $108 million package of emergency food and medical aid to the Soviet Union Tuesday but stressed that its policy of withholding ordinary assistance from Moscow remains unchanged.

Japan is making its first offer of food aid to the Soviet Union as a humanitarian gesture, Prime Minister Toshiki Kaifu said.A longstanding dispute over the ownership of small islands off northern Japan has prevented Tokyo and Moscow from signing a treaty to formally end World War II hostilities.

Foreign Ministry spokesman Taizo Watanabe said Japan's basic position on economic assistance to the Soviet Union remains unchanged but that humanitarian aid is being offered because the "situation is deteriorating very rapidly."

The package consists of $3.8 million in food aid and an equal amount in medical aid, both to be delivered through the Red Cross; up to $100 million in food credits through the Export-Import Bank of Japan and government tax support for organizations that help the Soviet Union.

The ministry had delayed deciding on food aid because of reports of a bumper Soviet harvest. But Watanabe acknowledged that problems with transportation and organization had created food distribution problems.

The European Community has pledged $2.8 billion in aid to the Soviets, and the United States will extend the Soviets $1 billion in agricultural credits.