Gabriel told guests in the SPD's headquarter in Berlin that Brandt's gesture of German contrition in Warsaw in 1970, when he kneeled before a memorial to the Jewish ghetto, acknowledged German guilt over the Nazi-era and initiated new trust among countries neighboring post-war then-divided Germany.

That levelled the way, Gabriel said, toward Germany's eventual reunification in 1990 - after the 1989 fall of the Berlin Wall.

Gabriel said Brandt was an early advocate of the European Union. His one-time appeal to the public to "dare [to push for] more democracy" remained a lasting legacy, Gabriel added.

Last Wednesday, a separate memorial event was held in Brandt's hometown Lübeck where around 1,500 guests gathered in the Music and Congress Hall to honor the former chancellor.

"Willy Brandt is still present - with everything that he embodied: his love of freedom, and his quest for peace and justice," German President Joachim Gauck told that audience.

Brandt's legacy

Born Herbert Frahm in 1913, Brandt is widely considered one of the greatest European statesmen of the 20th Century.

A staunch opponent of the Nazis, Brandt left Germany in 1933 after Hitler took power. In exile, Frahm began living under the pseudonym Willy Brandt, a name he later officially adopted to avoid detection by occcupying Nazi-German troops.

After World War II, Brandt helped rebuild West Germany's Social Democrats (SPD).

He served as mayor in divided Berlin from 1957 to 1966, helping lead the city's western sectors through the crisis sparked by former communist East Germany's building of the Berlin Wall.

Germany's first post-war SPD chancellor

In 1969 he was elected Germany's first Social Democratic chancellor since 1930.

Brandt resigned as chancellor in 1974 when it was discovered that Günter Guillaume, a spy for East Germany, had made his way into the tight circle of the chancellor's closest advisers.

Brandt remained the leader of the SPD until 1987.

Remembered for 'Ostpolitik'

Brandt is remembered by many for his efforts to achieve reconciliation between West Germany and the countries of the Soviet Bloc. This policy, known as Ostpolitik, contributed to him winning the Nobel Peace Prize in 1971.

In 1970, Brandt's visit to Poland gave rise to what many consider a defining moment of his chancellery.

As he laid a wreath at memorial to the Jewish ghetto of Warsaw, he unexpectedly fell to his knees and remained there for more than a minute.

The pictures of what became known as the Warsaw Genuflection traveled around the world, and became one of the best-known images in modern German history.

Brandt died in 1992 in Unkel near Bonn.

ccp/kms, ipj (AFP, dpa)