The environmentalist Greens in the northern German port city have cleared the way for talks with the conservative Christian Democrats (CDU) about creating what would be the first-ever coalition between the two parties in Germany.

After party debate on Thursday evening, the majority of Green Party leaders decided to accept a CDU invitation to discuss a new “black-green” coalition.

“If we don’t position ourselves, it will be a sign of weakness,” said Hamburg’s Green party chief Anja Hajduk at the meeting.

Party members stressed that they won’t allow the possible coalition to put a price on key Green positions on the environment, education, and social welfare — topics on which they will likely be at odds with the more conservative CDU.

Some critics have warned Green party members that a coalition would be disadvantageous, saying the party would only be an “ornamental fig leaf on a black background.

The two parties are only considering the partnership because Hamburg’s election on Sunday yielded a victory for Angela Merkel’s conservative Christian CDU, but the party lost its parliamentary majority. Meanwhile the CDU’s traditional coalition partner, the pro-business Free Democratic Party (FDP), didn’t win enough votes to earn any parliamentary seats.

The Greens have plans for another meeting on the Thursday after the “black-green” meeting for further discussion of the coalition.

After the meeting Greens delegate Farid Müller said the CDU will have to make a generous offer. “Just a few nice nuggets won’t do,” he said. Otherwise the Greens won’t be able to reach a consensus on creating the coalition.