The trio of world leaders who orchestrated the reunification of Germany returned today to the city where the Cold War collapsed with the simple breach of a steel and concrete wall 10 years ago.

The mood was triumphant as former president George Bush, former German chancellor Helmut Kohl and Mikhail Gorbachev, the last president of the Soviet Union, were honored at a lavish ceremony at city hall. But the celebration was tempered by the recognition that the dream of a united, democratic Europe that seemed so close a decade ago has yet to be realized.

"After all we've been through, we still have much to do to secure the values of freedom and prosperity in Eastern Europe," Bush declared at the ceremony also attended by Kohl and Gorbachev, whose collaboration helped ensure a peaceful end to four decades of East-West confrontation.

Added Gorbachev at another point in his visit here: "Now, 10 years after, we see the world does not appear as we had hoped. Europe is no longer divided, at least not in the old sense of the word, but one cannot call it united by any means."

The reunion of three leaders here has become the centerpiece of anniversary celebrations marking the collapse of the Berlin Wall 10 years ago Tuesday. The fall of the Wall was the signature event in a year in which tens of millions of people were freed in Poland, Hungary, the former country of Czechoslovakia and farther east. It would lead to the reunification of Germany and an end to Europe's post-World War II division within a year.

Across the continent, there is genuine appreciation that the triumph of free-market democracies has improved living standards on both sides of the former Cold War divide. But while prosperity and freedom have reached places once dominated by repressive totalitarian regimes, there is still anxiety about growing disparities between rich and poor, and about a settling of old scores--between Communist and non-communist, between one ethnic group and another.

In the view of many politicians, business leaders and academic experts, the revolution of 1989 is still passing through a perilous transition. Besides coping with the dangers of ethnic warfare that has spilled so much blood in the Balkans, Europe still confronts economic and psychological barriers between East and West.

Indeed, many of the remarkable political and economic gains made by onetime Soviet Bloc countries such as Poland, Hungary and the Czech Republic--as well as their entry into NATO--have been undercut by the policy failures that contributed to the bloody fragmentation of Yugoslavia and the corruption and organized crime that threatens to snuff out Russia's hopes for establishing a successful free-market democracy. While some former Soviet Bloc states have prospered in the new Europe, others such as Bulgaria and Romania still lag far behind.

"I'm afraid we may have missed the boat," said financier George Soros, who has poured more than a billion dollars of his money into Central and Eastern Europe in the past decade. "We had an historic opportunity 10 years ago to help these people make a clean break with communism, and I believe we have failed to rise to the occasion."

Soros lamented the decision by Western governments to hand custodianship of Russia's transition to the International Monetary Fund. He says it was clearly impossible for Russia to fulfill the IMF's strict economic criteria. Now that this mistake has been recognized, Soros said, it may be too late because xenophobic forces are too ascendant for Moscow to think about accepting guidance from the West.

Within Europe, no country's national destiny has been transformed more than Germany's. With 82 million citizens reunited, the country sees itself as an anchor of stability in Central Europe that enjoys friendly relations with all nine neighbors for the first time in modern history. Internally, however, Germany is grappling with a lingering economic downturn that many economists blame on the costs of reunification. And it still has not surmounted "the wall in people's minds"--the political, economic and psychological division that separates residents of the country's eastern and western halves.

That divide provided an ironic counterpoint to the festive gathering of former leaders in Berlin today, when East Germany's last head of state, who was responsible for opening the Wall, was sentenced to more than six years in prison after losing an appeal of his sentence for complicity in the killing of people who tried to flee the country.

Egon Krenz, who succeeded Erich Honecker in October 1989 and then sought in vain to salvage the German Democratic Republic by loosening its barriers with the West, denounced the verdict as a political judgment that unfairly branded him the scapegoat for his country's failings.

"I will wear my prison uniform with more honor than certain judges do their robes," Krenz said after hearing the verdict. "I am ready to take political responsibility for my country but not for the Cold War. The border was not between the two German states but between NATO and the Warsaw Pact."

Gorbachev, who will address the German Parliament at the Reichstag on Tuesday, criticized the trial and said it was not proper for a Western court to pass judgment on an entire historical era. "We should put this all behind us," the former Soviet leader said. "We should look to the future instead of holding witch hunts."

Despite Germany's economic and political problems, fears among its neighbors about a resurgence of past imperial ambitions have proved unfounded.

"Germany today is a stable, sensible and dynamic democracy," said Israeli Prime Minister Ehud Barak, who became the first foreign leader to visit Berlin after the government moved here in September. "Nobody seriously fears any longer that Germany will become engaged in the big-power manipulations of the past."

To offset those fears, Germany bowed to the wishes of France and other neighbors to surrender the stable German mark in favor of a continental currency known as the euro. It is used in transactions among financial institutions and will become the everyday currency for 11 countries in the Euroland area in 2002.

To the east, Poland, Hungary and the Czech Republic have made remarkable gains in restoring their historical connections to the West. They have become the first former communist countries to join NATO, succeeded in adapting to the rigors of a free-market economy and seem poised to enter the European Union, possibly by 2003.

Even to these countries, however, economic success has come more slowly than anticipated. "Ten years ago, we were much more optimistic, or perhaps more naive, than we are now," said Jan Svejnar, economics adviser to Czech President Vaclav Havel. "While we are pleased at how democracy has taken root, there is some disappointment that the economic progress we anticipated could not be realized as fast as we would have liked."

But Svejnar predicted that over the next decade, Central Europe could experience an economic boom, arguing that the ingredients are in place for an extraordinary leap forward, one that could shift the dynamics of the European axis eastward.

"Once Germany has adjusted its economy to the demands of globalization, this entire region could really take off," Svejnar said. "Instead of looking at Europe as an East-West split, people may see a northeast pole centered around Germany as the new source of affluence, with the southern periphery of Mediterranean states left behind."

To the north, the Baltic states of Latvia, Estonia and Lithuania have also achieved extraordinary progress in moving out of Moscow's orbit. With the help of Finland and other Scandinavian neighbors, they have modernized their economies with the latest technologies and found ways to accommodate their sizable Russian minorities.

CAPTION: Former president George Bush, his wife, Barbara, and Mikhail Gorbachev join Berlin celebration.