German chancellor Angela Merkel's conservatives and the centre-left Social Democrats are starting talks on forming a new government.
It marked an attempt to break an impasse more than three months after the country's election.
Mrs Merkel's conservative Union bloc and the Social Democrats have run Germany together for the past four years.
But the Social Democrats vowed to go into opposition after a disastrous election result on September 24, and only reluctantly reconsidered after Mrs Merkel's attempt to build a coalition with two smaller parties collapsed in November.
The effort to form a government has already become post-Second World War Germany's longest.
Leaders aim to decide by Friday whether there is enough common ground to move on to formal coalition negotiations, which would require approval by a Social Democrat congress.