Erstwhile Soviet President Mikhail Gorbachev claims to have prevented Third World War in 1989 by not ordering troops to crush the demonstrations that proceeded the fall of the Berlin Wall.

Gorbachev is hailed in the West for ignoring hardliners who advised him to guarantee the Soviet Union's future by crushing a growing wave of dissent in Eastern Bloc countries which led to the fall of the Berlin Wall in 1989.

Now, 20 years on, the 78-year-old has said that had the Kremlin used troops to crush the demonstrations, it would have sparked a catastrophic set of events and even the Third World War.

"If the Soviet Union had wished, there would have been nothing of the sort (the fall of the Wall) and no German unification. But what would have happened? A catastrophe or World War Three," 'The Scotsman' quoted Gorbachev as saying.

He added: "My policy was open and sincere, aimed at using democracy and not spilling blood. But this cost me very dear."

Most Russians revile Gorbachev for his weakness in allowing the collapse of the Soviet Union and the loss of Moscow's global empire. A poll last year found that 60 per cent of Russians still viewed the demise of the Soviet Union as a "tragedy".

Thousands of East Germans crossed to West Berlin in November 1989 after the Soviet-backed authorities unexpectedly ordered the opening of tightly guarded border crossings in the Berlin Wall.

Gorbachev, who could have used nearly half-a-million Soviet troops stationed in East Germany to crush the rebellion quipped that he had "a good night's sleep" after the Wall was actually opened.

"I am very proud of the decision we made. The Wall did not simply fall -- it was destroyed just as the Soviet Union was destroyed," he said.