The North Atlantic Treaty Organization warned of "most serious consequences" for the Soviet Union, its neighbors and the international community if Moscow does not pursue the path of reform initiated by Gorbachev.
A statement by NATO Secretary-General Manfred Woerner said the 16 allies "are deeply concerned that the latest developments foreshadow a grave deviation from the path of reform and the rule of law in the Soviet Union."
An emergency meeting of the alliance's foreign ministers was planned for today or Wednesday.
Europe's smaller countries reacted to the Soviet coup with concern.
"My reaction is one of bitter disappointment," said Irish Prime Minister Charles Haughey in a radio interview. "Anybody who cherishes freedom and a stable, peaceful world must regard this as a black day. The scenario, I don't think, could be much worse."
In Austria, Chancellor Franz Vranitzky said Gorbachev's reforms "can't all be reversed, and that is possibly a glimmer of hope for the future."
The Finnish government said it "deplores the fact that the calling of a state of emergency has halted the development toward democratization" for its giant neighbor.
Denmark vowed to seek a European Community freeze of all aid and cooperation with the Soviet Union until the situation there is clarified.
"The point has been passed at which one can put the genie back in the bottle," said Danish Foreign Minister Uffe Ellemann-Jensen. "The genie--freedom and democracy--has slipped out, and it will be very hard to stuff it back in again."
Sweden said it is prepared to take in up to 10,000 Soviet asylum-seekers should refugees flood in across the Baltic Sea.