BERLIN (Reuters) - Germany s Greens on Saturday all but ruled out a three-way coalition with Chancellor Angela Merkel s conservatives and the pro-business Free Democrats (FDP) after the Sept. 24 election and a conservative said such an alliance would not be ideal. Polls show Merkel s conservatives are likely to win the election with around 38 percent of the vote but will be left in need of a coalition partner. Their rival Social Democrats (SPD) are lagging on around 22 percent. Possible coalition options include a repeat of the current  grand coalition  between the conservatives and SPD or a  Jamaica coalition  of the conservatives, FDP and Greens - the name referring to the black, yellow and green colors of the Jamaican flag. Katrin Goering-Eckhardt, one of the Greens  two top candidates, told regional newspaper Passauer Neue Presse:  I can t imagine Jamaica.  Coalitions tend to be tested at the state level before they are formed at the national level. A Jamaica alliance was formed in the coastal state of Schleswig-Holstein after Merkel s Christian Democrats (CDU) won an election there in May. But Goering-Eckhardt said the Greens and FDP had  diametrically opposed positions  on issues including climate protection, emission thresholds for clean cars and refugees.  I can t see how it could work at the national level,  she said. FDP leader Christian Lindner told Focus magazine he was also unable to envisage a Jamaica coalition given the hurdles to reaching agreement with the Greens on immigration and energy. Interior Minister Thomas de Maiziere, a senior conservative, told regional newspaper Rheinische Post neither the conservatives nor the SPD wanted to continue the current  grand coalition  because it  is not good for democracy , referring to the small parliamentary opposition that such a tie-up leaves. But he added that it would be harder to reach agreements with the Greens and FDP on domestic security than it has been with the SPD.  From a security perspective it would be good if the conservative bloc could choose a two-way alliance,  he said. Cem Ozdemir, the Greens  other top candidate, said in an interview with Tagesspiegel am Sonntag newspaper that his party wanted to be in the next federal government, which he suggested would be formed by Merkel:  The race for first place seems to be over - Angela Merkel is out in front.   But the latest polls show Merkel s conservatives and the Greens would not be able to muster enough support between them to form a two-way alliance. While support for the Greens has dropped to single digits this year - it is on 8 percent in the latest polls - a Forsa survey published this week showed half of Germans would welcome the Greens being part of the post-election government. Merkel on Saturday reiterated her warning to voters about a coalition between the SPD, radical Left party and Greens, telling voters in the southwestern city of Reutlingen that a red-red-green tie-up would be  bad for our country  and Germany should not embark on any experiments at a time of uncertainty. A red-red-green alliance, which had seemed a possible option early this year, has not been able to get a majority in polls for weeks. 