Germany's center-left Social Democrats are debating whether to enter coalition talks with Chancellor Angela Merkel's conservatives, and help break the political deadlock since September's election.

If the Social Democrats reject entering the talks, the only options left are for Merkel to form a minority government or for new elections.

Social Democrat deputy leader Malu Dreyer, the Rhineland-Palatinate governor, told delegates in Bonn on Sunday that since Merkel's Union bloc has indicated it wouldn't form a minority government, their vote will either be for entering talks on forming a new so-called "grand coalition" with the chancellor, or new elections.

Urging the delegates to vote for entering coalition talks, she told them "we can't force the Union into a minority government, that's an illusion."

The vote is expected later Sunday.