Some 35,000 people marched through the streets of Hanover on Saturday (April 23) to protest against a sweeping European-US trade deal, police said. Organisers put the number of attendees at around 90,000.
The protest against the Trans-Atlantic Trade and Investment Partnership (TTIP) was organised a day before the visit by the US President Barack Obama.
He is set to promote the deal at Hanover's trade fair on Sunday (April 24) in a joint bid with German Chancellor Angela Merkel to revive the momentum behind the agreement, which top trade officials hope to push through this year.
Demonstrators took to the streets of the northern German city bearing placards and banners calling on politicians to "Stop TTIP and CETA" - an EU-Canada trade deal that looks set to come into force in 2017.
Public scepticism in Germany has clouded the TTIP negotiations from the start, but support for the deal has plunged to new lows in recent months.
A YouGov survey showed on Thursday (April 21) that only 17 percent of Germans believe the free trade deal is a good thing, down from 55 percent two years ago. Many Germans fear the deal will lower standards for products, consumer protection and the labour market.
German officials said ahead of Obama's visit they remained optimistic that a broad "political agreement" between Brussels and Washington could be clinched before Obama leaves office in January. The hope is that TTIP could then be finalised with Obama's successor.