Social Democrat leader Olaf Scholz has said he wants to form a new government before Christmas.
Germany's four biggest parties have held a series of bilateral meetings on Sunday to communicate their positions before deciding on further steps in forming a new government.
The centre-left Social Democrats, who won Germany's national election last month, first met with the Free Democrats before holding talks with the Greens.
The latter two had already met on September 29, though it is unusual for smaller parties to make the first move.
The sessions in Berlin — that some observers described as akin to a political "speed dating" — were rounded off by a meeting between the Free Democrats and the CDU/CSU, which suffered a narrow defeat on September 26.
All representatives insisted they held "constructive" talks but refused to give details so as not to jeopardise negotiations.
Social Democrat leader Olaf Scholz has said he wants to form a new government before Christmas. He currently stands the best chance of succeeding Merkel as chancellor after 16 years in office.
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