Conservative chancellor Angela Merkel, whose fourth term was plunged into doubt a week ago when three-way coalition talks with the pro-business Free Democrats (FDP) and Greens collapsed, was handed a political lifeline by the SPD on Friday.
Hubertus Heil, the party's general secretary, said: "The SDP is deeply convinced there should be discussions".
If Merkel can't put together a coalition, the only options would be a minority government or a new election, months after the September 24 vote.
Talks with the SPD should be based on "mutual respect" and "compromise", she added. "The people have voted, and I absolutely do not favour, if we can't do anything with the result, asking people to vote again", Merkel said on Saturday at a party conference of her Christian Democratic Union (CDU) in Kuehlungsborn, northeast Germany, Xinhua reported citing Focus Online.
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If the two sides can't reach an agreement by then, "the conservatives should aim for a minority government", Paul Ziemiak, head of the CDU youth, was quoted as saying by the Bild newspaper.
Seehofer said the SPD must not set too many conditions.
Speaking in Kuehlungsborn in the northern state of Mecklenburg-Vorpommern, Merkel said Germany's politicians had a responsibility to work with the September results.
The Social Democrats centred their campaign on building a more socially just Germany, pledging more investment in education and infrastructure.
Although Mr Schulz painted the move to open talks as a response to Mr Steinmeier's appeal, he was facing the possibility of a leadership challenge over his refusal to open talks with Ms Merkel.
An Emnid poll showed on Sunday that 52 percent of Germans backed a grand coalition.