HELSINKI, Finland--Soviet President Mikhail S. Gorbachev said yesterday that Moscow will cut its nuclear forces in the Baltic Sea and will destroy four aging submarines and the nuclear missiles they carry.

Gorbachev also said the Soviet Union has removed all tactical nuclear missiles that could strike the northern European region and will take certain types of sea-launched nuclear weapons out of the Baltic Sea.

In a 45-minute speech to Finnish business leaders, politicians and other guests on the second day of a three-day visit to Finland, Gorbachev repeated his hope to eliminate nuclear weapons from the 148,600-squaremile Baltic Sea.

"We are prepared to come to agreement with all the nuclear powers and the Baltic states on effective guarantees for the nuclear-free status of the Baltic Sea," he said in a nationally broadcast speech in Helsinki's Finlandia Hall.

Gorbachev said the Soviet Union was taking the steps unilaterally, dropping previous conditions that Western countries first agree to a nuclear-free zone.

In Washington, White House press secretary Marlin Fitzwater said, "We do not believe nuclear-free zones contribute to security in Europe.

"Most of these proposals have been designed to affect NATO deterrence capability while leaving Soviet nuclear weapons intact," Fitzwater said. "On the other hand, we do appreciate the intent of this and if it can develop into something concrete, why, that might be a hopeful sign."

Later, Fitzwater revised his remarks, saying, "In fact we do not consider this a hopeful sign."

Gorbachev said the steps were a follow-up to a speech he gave two years ago in the Soviet Union's northern port of Murmansk, in which he first proposed a nuclear-free zone in northern Europe. Two NATO countries in the region, Norway and Denmark, do not permit nuclear weapons in their territory in peacetime.

Gorbachev said the Soviet Union already has taken two of its six Golf-class submarines out of operation from the Baltic Sea and pledged to destroy the remaining four by the end of next year.

In his Murmansk speech, Gorbachev had offered to remove nucleararmed subs from the Baltic Sea and Soviet officials offered to withdraw the remaining four only if countries of the region agreed "on a non-nuclear North."

Yesterday, he dropped that requirement.

"The Soviet Union started by removing from operational status two Golf-class submarines and before the end of 1990 it will destroy the four remaining submarines of the same class," he said.