Egon Bahr, one of the key architects of "Ostpolitik", credited with easing tensions during the Cold War and smoothing the path to German reunification, has died aged 93, his party said Thursday.
Bahr, who died late Wednesday, served as a close advisor to former West German chancellor and Nobel peace laureate Willy Brandt and spearheaded his drive to establish ties with the Soviet Union and communist East Germany.
Sigmar Gabriel, head of the Social Democratic Party (SPD), the junior partner in Germany's coalition government, hailed Bahr as a great "politician for peace".
"He believed deeply in the power of freedom and the might of conversation -- that was the foundation of the 'change through rapprochement'" Bahr championed, Gabriel wrote on his Facebook page.
Chancellor Angela Merkel, a conservative who grew up in East Germany, in a statement hailed Bahr's "valuable contribution to change and detente in East-West ties".
"Few politicians are lucky enough to change the world with an idea and to be able to witness how their own vision becomes reality in their lifetime," Foreign Minister Frank-Walter Steinmeier said.
Steinmeier, also a Social Democrat, said that the "radically new Ostpolitik" pioneered by Bahr "quite literally changed the course of history and made German and European unification possible".
Bahr had travelled to Moscow as recently as late July to meet with former Soviet leader Mikhail Gorbachev to discuss ways to reduce tensions between Moscow and Berlin over the Ukraine crisis.
However, critics, including Steinmeier, denounced his initiative as too conciliatory toward Russian President Vladimir Putin.
Early in the Cold War, Bahr rejected muscular foreign policy and displays of military strength as a response to the threat posed by Moscow in favour of a "policy of small steps" based on gestures of detente and dialogue.
His vision paved the way for West German accords with the Soviet Union, satellite states of the Eastern bloc and finally East Germany.
Many historians said the approach laid the foundation for Gorbachev's perestroika reforms and the fall of the Berlin Wall in 1989.
Bahr, who began working for Brandt when the latter was mayor of West Berlin, met with US President John Kennedy during his 1963 visit to the city when the American delivered his iconic "Ich bin ein Berliner" speech.
Bahr recalled during 50th anniversary celebrations two years ago that Germans instantly understood the message of Kennedy's "explosive" words, calling them "an unwritten pact" with Soviet leader Nikita Khrushchev.
"Berliners knew instinctively that they could feel safe," he said.