BERLIN, Nov 12 (Reuters) - The Greens, Germany's third biggest political force, aim to poach votes from Angela Merkel's conservatives in next year's federal election, they said on Monday, after selecting new leaders with broad middle-class appeal.
The Greens rejected suggestions they had chosen their twin candidates with an eye on a coalition with Merkel's Christian Democrats (CDU) and their CSU Bavarian allies in 2013 instead of with the centre-left Social Democrats (SPD).
"We are not campaigning for a coalition with the CDU/CSU, we want to poach their voters," party co-chairman Cem Oezdemir told a news conference.
In Saturday's primary, the Greens chose former environment minister Juergen Trittin, their parliamentary leader and undisputed strategic leader, to spearhead the 2013 campaign.
But the choice of quietly-spoken east German Katrin Goering-Eckardt, a leader of the Lutheran church, to run with him came as a surprise.
The party has its origins in the peacenik ecologist movement of the late 1960s and '70s but has long been part of the German political establishment and was in government with the SPD from 1998-2005. True to its feminist roots, all leadership posts are shared by a man and a woman.
The Greens are in third place in polls behind Merkel's conservatives and the SPD, making them possible kingmakers in the election.
Both Trittin, 58, and Goering-Eckardt, 46, the deputy speaker of the Bundestag lower house of parliament, are on the party's moderate wing. Trittin takes a deep interest in the euro crisis, foreign and financial policy and is reported to have his eyes on the post of finance minister.
But the Greens' traditional allies in the SPD - who swapped sides themselves from 2005-2009 when they were Merkel's junior coalition partners in her first term - appear to distrust the environmentalists' motives in shifting to the centre.
SPD leader Sigmar Gabriel challenged the party on Monday to commit itself to a so-called "Red-Green" coalition in 2013. But Oezdemir shot back that perhaps the SPD should concentrate on how to take away votes from the conservatives.
"Perhaps Mr Gabriel has work to do in his own party," said Oezdemir, who shares the party chair with the colourful Claudia Roth, who was defeated in the party primary on Saturday.
Trittin told German radio on Monday his party preferred the SPD and could not imagine an alliance with the conservatives or their Free Democrat (FDP) allies due to differences on Europe and social policies, but did not go as far as ruling it out.
Support for the Greens jumped to historic highs of 15-20 percent in polls after the Fukushima nuclear disaster in Japan, but dropped thereafter as they struggled to differentiate themselves from the two big parties. Merkel converted to the anti-nuclear cause after Fukushima and is now in a hurry to shut down atomic power plants.
The Greens are now polling about 14 percent, after scoring 10.7 percent in the 2009 election. (Additional reporting by Thorsten Severin; Writing by Stephen Brown, Editing by Gareth Jones)