Thousands of demonstrators have turned out in the city of Hannover to protest a planned US-Europe free trade agreement a day before President Barack Obama arrives.
Police said that more than 20,000 people gathered for the demonstration.
Many in Germany regard the planned Trans-Atlantic Trade and Investment Partnership (TTIP) with suspicion.
Protesters carried placards with slogans such as "Yes We Can - Stop TTIP!"
Proponents argue the agreement would boost business at a time of global economic uncertainty but critics worry it would erode consumer protection and environmental standards.
Officials in Washington and Europe are trying to clinch key parts of the TTIP deal before the end of the year. Mr Obama is due in Hannover on Sunday to open an annual industrial fair.