Wowereit comfortably won the mayoral election on September 18, but his party did not secure enough seats in the state parliament to govern outright. Tuesday's announcement left Wowereit at an impasse.
His Social Democratic Party is in favour of the extension, but their favoured coalition partner is the Green party, want the motorway extension in the south-east of the city stopped.
The project, which involves partially closing an incomplete motorway ring around the city and cutting a path through residential areas and parks, has been put on ice as the negotiations continue. The SPD and the Greens suggested using the money from the federal government elsewhere, but the Transport Ministry has now ruled that out.
The ministry said it was not possible because there were no other major construction projects in the city. Andreas Scheuer, parliamentary state secretary in the construction ministry, told the Berliner Morgenpost paper, “We're not a request show. The A100 is an important project for us.”
The Green party would like to use the €420 million set aside for the motorway to improve roads in the area and install noise reduction facilities.
The extension has been a contentious issue in Berlin for some time.