BERLIN (Reuters) - Support for Germany’s opposition Greens has fallen to its lowest level in almost 15 years, a Forsa poll showed on Wednesday, hitting the chances of a left-leaning coalition snatching power from Chancellor Angela Merkel in September’s election.

The survey for magazine Stern and broadcaster RTL showed the Greens shedding one point to 6 percent - its weakest reading in that poll since August 2002. That leaves it hovering just above the 5 percent threshold that parties need to enter the national parliament.

Another survey by pollster INSA published on Wednesday also showed the Greens on 6 percent - behind the Free Democrats (FDP) who were on 6.5 percent and so on track to return to parliament after crashing out of it in the 2013 election.

Some polls have suggested a left-leaning ‘red-red-green’ alliance of the Social Democrats (SPD), the far-left Linke party and the environmentalist Greens could emerge after a Sept. 24 election.

The Forsa survey showed Merkel’s conservatives unchanged compared with the previous week on 36 percent while the Social Democrats remained on 30 percent.

The far-left Linke gained one point to 9 percent. It also improved by half a percentage point in the INSA survey to 9 percent.

The anti-immigrant Alternative for Germany (AfD) was unchanged in both surveys, on 8 percent in the Forsa survey and 10 percent in the INSA survey. The party has lost momentum as migrant arrivals have dropped, infighting has taken hold. The SPD has picked up since naming Martin Schulz as its candidate to run against Merkel.

But even support for him seems to be waning - the Forsa survey showed support for Schulz under the 30 percent level in that poll for the first time since being nominated as the SPD’s candidate. If there were a direct vote for chancellor, 29 percent would pick him - 3 percentage points below the previous week’s level.

That compares with 44 percent of Germans who would vote for Merkel in such a direct vote - 1 point more than last week.