Germany's President Joachim Gauck is visiting Poland to mark 25 years of a treaty that laid foundations for friendly ties between the two neighbors locked in troubled past.

Gauck and his partner, Daniela Schadt, were greeted Friday by Poland's President Andrzej Duda. The ceremony was to be held in the Presidential Palace's front yard, but was moved indoors due to a rainstorm.

Gauck will also meet Prime Minister Beata Szydlo for talks on European security, next month's NATO summit in Warsaw, the migrants crisis in Europe, Britain's referendum on European Union membership and bilateral issues.

On June 17, 1991 German Chancellor Helmut Kohl and Poland's Prime Minister Jan Krzysztof Bielecki signed a good-neighbor treaty between nations burdened by memories of Germany's World War II aggression against Poland.