The Soviet Union on Wednesday drastically cut the value of its currency on a key exchange rate, offering more than four times more rubles for a dollar and taking a step toward opening its money for international trade.

The new rate - 27.6 rubles per dollar - roughly corresponds to black market dealings.Foreign currency exchange offices throughout Moscow were closed Wednesday as employees besieged the Gosbank state bank for details of the changes.

The foreign currency office at central Moscow's Belgrade Hotel posted the new rates Wednesday but put a sign on its counter saying it was "closed for technical reasons." A Western reporter said he changed money Wednesday at the new rate in Kiev, the Ukrainian capital.

The new rate is part of a currency reform law that took effect Monday. The government initially announced it would apply only to Soviet citizens seeking to travel abroad or emigrate, and those who are allowed to purchase small amounts of foreign currency.

But foreigners will also be entitled to buy rubles at the more favorable rate, said Alexander Polyakov, a manager at the government's Vneshekonombank, the foreign affairs bank.

Polyakov said in an interview that his bank was scrambling to calculate the exchange rate for a wide range of foreign currencies because the state bank gave it only the ruble-dollar rate.

The ruble is all but worthless outside Soviet borders. Artificially set exchange rates have hampered Soviet efforts to join the world economy.

The new "auction" or "market" exchange rate will change twice a week following currency auctions at the state bank, Polyakov said.

Polyakov said instructions were being sent to all foreign exchange offices. He did not know when they would reopen.