Merkel responded shortly after the result, saying she "welcomed" that the SPD cleared the way for formal coalition negotiations.

"It is important for us that Germany has a stable government," said the Chancellor Sunday evening at the CDU headquarters, adding that the exploratory talks paper is the framework for negotiation, "this will also require intensive consultations."

The special congress came after the SPD and the Union reached the breakthrough on Jan. 12 in exploratory talks with a 28-page document, and the two blocs now will kick off formal coalition negotiations in a few days.

SPD's "greenlight" policy also helped Germany avoid snap elections as Merkel said a minority government would not be an option. It is widely expected that snap elections will not address the political crisis but only make the far-right populist Alternative for Germany (AfD) stronger.

Schulz said French President Emmanuel Macron had told him in a telephone conversation on Saturday that France was afraid that the far-right politics could come to power in Germany if the German government did not work with its neighbor to support the European idea.

Schulz also promoted the historic political change in German European politics, putting an end to austerity and towards a stronger common responsibility for Europe.

"For me as a convinced European, this is a historic success," emphasized Schulz. "Without the SPD, there will be no bold momentum for the future of Europe."