The Soviet government Friday expanded the right to trade with foreigners from about 100 ministries and state enterprises to virtually all businesses in the country, the official news agency Tass reported.

The decree is a major deregulation in a country in which contact with foreigners was strictly limited until a few years ago and still causes police scrutiny in some locations.The move had been expected since the Council of Ministers announced in December that it would act to expand exports by spring.

Even cooperatives, the private businesses which share profits among members, are permitted to trade.

Foreign currency is still strictly controlled, and businesses that earn convertible currency expect it to be heavily taxed. The ruble is not convertible and the Soviet Union urgently needs foreign cash to buy Western technology.

Authorities are planning to allow Soviet businesses to buy convertible currency like dollars in a sealed-bid auction, said Alexander I. Potyomkin of the Foreign Economic Bank.

Businessmen are watching for this auction with great curiosity, as they expect a rate of 6 to 7 rubles to the dollar would be necessary to draw sellers. The official exchange rate is 10 times that.