LONDON -- Europe faced the disturbing prospect yesterday that the period of peace and cooperation between the Soviet Union and the West may have come to an end with the overthrow of Mikhail S. Gorbachev by hard-line Communists in Moscow.
The North Atlantic Treaty Organization met in emergency session in Brussels, Belgium, and the foreign ministers of the European Community scheduled a meeting for today in the same city to consider the political and, possibly, military consequences of the crisis in the east.
After their meeting last night, the NATO countries issued a statement praising Mr. Gorbachev for policies that "have led to the end of the Cold War era."
The statement called on the new Soviet leadership to "adhere fully to its international commitments and obligations" and said that the allies "are determined to ensure that the achievements of the last years in all fields of international policy . . . are not reversed."
But as word of the imposition of a six-month emergency rule came out of Moscow, it was almost a certainty that -- with the major exception of Germany's -- Western aid programs won by Mr. Gorbachev during his years as head of the Soviet state
would be re-examined with the aim of putting them on hold.
Most recent among those gains was an associate membership for the Soviet Union in the International Monetary Fund and World Bank -- given during the Group of Seven summit here in July -- and the possibility that most-favored-nation trade status would be granted by the United States.
Also, hundreds of millions of dollars in assistance from the European Community may now be in jeopardy.
An EC technical assistance package worth nearly half a billion dollars, signed last week, will be re-examined by the EC foreign ministers when they meet today in The Hague, Netherlands, though it is not at all certain they will stop it, an EC official in London said.
Only in Germany, whose program of assistance to the Soviet Union dwarfs all others, did the promised aid package still seem secure yesterday.
In seeking to rid the former East Germany of Soviet troops that once numbered 380,000 and Soviet nuclear weapons, Bonn has forged probably the closest economic links of any country with ++ the Soviet Union.
It has pledged $17 billion in loan guarantees, credits and housing for returning soldiers.
Yesterday, Finance Minister Theo Waigel said the economic commitments would stand firm, as he expected Moscow's pledge on troop withdrawal to stand.
"They weren't just given in a lump, but according to a schedule of things that have to be carried out. The Soviet Union will carry out its side, and we will carry out our side," Mr. Waigel said.
Germany, with 270,000 Soviet troops still in the eastern part of the country, is the NATO country most likely to be directly affected by an upheaval in the Soviet Union. Possibly for that reason, Foreign Minister Hans-Dietrich Genscher put the most hopeful spin yesterday on what the events in Moscow will likely bring.
In a statement released by the Foreign Ministry in Bonn, Mr. Genscher reminded those responsible for governing the Soviet Union that the country, by signing the charter of the Council on Security and Cooperation in Europe in 1990, had "accepted the principles of democracy and the principle of free elections."
In London, British Prime Minister John Major came onto the sidewalk of No. 10 Downing Street, his residence, and described what had occurred in Moscow during the night as an "unconstitutional seizure of power." He later met with his Cabinet in emergency session.