Hamburg  - The German Greens agreed Wednesday to their first state coalition ever with Chancellor Angela Merkel's Christian Democratic Union (CDU), according to a Greens official, Antje Moeller.

The two parties, formerly deadly rivals, had agreed after weeks of negotiations on broad terms to jointly rule the city-state of Hamburg, one of the 16 German states.

An accord would be widely seen as a boost to Merkel, since a successful alliance with the Greens at state level might encourage her to ditch her current partner, the Social Democrats, if friction in the federal coalition were to become too great.

Emerging from a 12th round of talks, Moeller, who oversees interior policy, said, "There's nothing more for the plenary panel to settle."

She did not disclose the terms of the compromise, adding that fine tuning would take place on Thursday.

Before the meeting, the centre-right CDU and the environmentalist Greens had been at odds over plans to build a big coal-fired power station next to the city's river, the Elbe, and to dredge a deeper channel in the river so the biggest ships can reach the port. (dpa)