Müller was re-appointed Berlin mayor for a five-year term on Thursday, winning 88 votes in the 160-seat Senate of a growing city-state of 3.6 million. One-in-four of its residents has foreign roots.

Metropolitan Berlin, aside from becoming federal capital from 1999 - in the wake of German reunification - is one of Germany's city-states.

Before his Senate election on Thursday, Müller signed a 187-page coalition deal with the city's ecologist Greens and ex-communist Left after hard talks focused on investments in infrastructure - despite hefty city debt.

Later on Thursday, Müller named his cabinet of 10 senators, including the Greens' leading candidate Ramona Pop who became regional economy senator.

"We have long worked to gain government participation in [regional] Berlin," said Pop.

Müller's governing three-way coalition holds 92 seats in the 160-seat Senate. 

Müller, himself, was re-elected with 88 votes - seven more than necessary - out of 158 cast on Thursday. Among them were two abstentions.

In opposition are the pro-business liberal Free Democrats, local deputies of Chancellor Angela Merkel's Christian Democrats (CDU) and, for the first time, the strident anti-foreigner Alternative for Germany (AfD).

SPD bruised

Previously, Müller, had governed Berlin with the CDU, which slumped to 17.6 percent - a drop of nearly 6 percent in September's poll. Müller's SPD fell to 21.6 percent - from 28.3 percent - but stayed on as the assembly's largest grouping.

The Greens garnered 15.2 percent, just 1 percent ahead of the upstart AfD.

For the Left, Thursday's signing marked a return to government after five years. Between 2001 and 2011, the Left was junior partner in two coalitions under Müller's SPD predecessor, Klaus Wowereit, who stepped aside in 2014.

"The tasks have become larger, but the scope to move has also become larger compared to 10 years ago," said local Left leader Klaus Lederer, who becomes senator for culture.

'Great doubt' whether governable

Stefan Evers, the general secretary of Berlin's local CDU, told regional RBB public public radio that he had "great doubt" that Müller, who turns 52 on Friday, would be able to handle the diverse policy planks espoused by the Greens, the Left and the SPD.

At election time, Merkel's Bavarian ally, the Christian Social Union (CSU) had railed against Left-Green-SPD constellation.

"Red-Red-Green and a leftist republic must not emerge," said CSU general secretary Andreas Scheuer in September, warning against such a model for next year's federal Bundestag election due in September 2017.

Preceding Müller's Berlin coalition by two years is Thuringia, another eastern German regional state, where a red-red-green coalition led by Left party premier Bodo Ramelow was formed in late 2014.

Investments planned

Despite a local "debt mountain" put at 60 billion euros ($64.4 billion) and 15 years of past spending austerities, Berlin's new coalition plans to invest several billion euros to create 55,000 apartments, modernize transport, ailing bureau equipment and dilapidated schools.

"We can now implement what was blocked over the past years," said Müller, referring to the growing city's stretched infrastructure.

FDP leader Sebastian Czaja described the spending plan of Müller's new government as "exorbitantly exaggerated."

Wowereit's nadir, the scandal-plagued and still unfinished Schönefeld international airport project on Berlin's southern outskirts, overran numerous deadlines and ran up unexpected costs.

ipj/kms (AFP, dpa, Reuters)