BERLIN (Reuters) - Chancellor Angela Merkel's conservative alliance has extended its lead over the Greens, two polls showed on Wednesday, as the ecologists' campaign to take the chancellery for the first time stumbles ahead of September's federal election.

The Greens surged ahead of the conservatives in polls in late April after they picked Annalena Baerbock as their candidate to run for chancellor, with her pitch for a "new start" capturing voters' imagination.