Hamburg - An unusual alliance between Chancellor Angela Merkel's Christian Democratic Union (CDU) and the left-of-centre Greens took office Wednesday in the German state of Hamburg.

The new state assembly re-elected Ole von Beust, 53, as mayor, the state premier's title, and then approved his choice of three Green and six CDU ministers. The two parties have never partnered before at such a high level.

The new coalition in Hamburg, one of Germany's 16 states, has signed a detailed accord on a mix of pro-business and green policies, and has been seen by some political scientists as a trial run for a later coalition between Merkel and the Greens at federal level.

Both parties deny grander plans. Apart from their common middle- class origins, they have been visceral opponents in the past.

Beust, who will be serving his third term of premiership, appeared to even win an opposition vote, with 69 of the 121 assembly members voting for him. His coalition controls
68 seats in the legislature.

The coalition was dictated by the CDU's loss of its absolute majority in the February 24 state election and the Merkel party's reluctance to make a pact with local Social Democrats.

Despite the national attention the coalition has won, Beust, a lawyer by profession who also currently chairs the Bundesrat upper house in Berlin, has disclaimed federal ambitions, saying his heart is in Hamburg.

Seen as an unreliable maverick force bent on upsetting the political establishment when they erupted onto the political landscape at the end of the 1970s, the Greens first took on coalition responsibility at state level from 1985, progressing to partnership in the federal government from 1998 to 2005.

But their partners were always the Social Democrats (SPD) - and their sworn enemies the conservative, traditionalist and deeply establishment CDU.

In Hamburg, the key bone of contention between the two is the city's Moorburg coal-fired power station already under construction by the Swedish utility company Vattenfall.

A Greens minister, Anja Hajduk, will be in charge of planning permission for it, but she may lack the legal means - or sufficient compensation funds - to block it, now that its foundations have been laid.

In exchange for 40 million euros (65 million dollars) in funding for environmental projects, the Greens reluctantly agreed to a CDU pet project: dredging the River Elbe so the largest container ships can reach the port of Hamburg. (dpa)