Helmut Kohl, 79, George Bush, 85, and Mikhail Gorbachev, 78, hailed their excellent relations at a Berlin cabaret on Saturday, 20 years after the Cold War leaders watched over the Wall's fall.

The German ex-chancellor (1982-1998), US former president (1989-1993) and last Soviet leader (1985-1991) took the stage to share their memories of 1989 in front of a silvery curtain at an historic cabaret venue the Friedrichstadtpalast.

"Mikhail Gorbachev and George Bush were Germany's most important partners," said Kohl, who has been wheelchair-bound since fracturing his hip in February 2008.

"There has never been a relationship that reached the level of my relations with these two gentlemen," he said.

The "chancellor of reunification," who speaks with difficulty after a stroke left his lower face partially paralysed, saluted Bush as someone to call if you wanted cheering up.

"If you were in a bad mood, you just had to pick up the telephone and call George Bush... I can assure you that he'd put you in a good mood," he said, to rapturous laughter from the 1,800 people present.

The audience included newly elected German Chancellor Angela Merkel, former Hungarian and Polish prime ministers Miklos Nemeth and Tadeus Mazowiecki, as well as ambassadors and other dignitaries.

Major celebrations are planned for November 9, marking 20 years since the Berlin Wall came down, heralding the collapse of Soviet communism and the reunification of Germany.

Saluting his "former colleagues," Bush, who also has difficulty moving since a hip operation in 2007, hailed Kohl as "truly a great statesman of the 20th century -- he was a rock, solid!"

"Nevertheless, the events of '89 were not set in motion in Bonn, Moscow or Washington, but in the hearts and minds of the people deprived for too long of their God-given rights," Bush said.