"The trust of the citizens is essential to make this important agreement happen," German agriculture minister Christian Schmidt said after discussing the Transatlantic Trade and Investment Partnership (TTIP) pact with officials in Washington.
The proposed TTIP "gives us big economic, regulatory and geostrategic possibilities -- but only if the citizens understand what it is about," he said.
During his two-day visit, Schmidt met his US counterpart Tom Vilsack and US Trade Representative Michael Froman.
Begun in July 2013, the US-EU TTIP negotiations are aimed at creating the world's biggest free-trade and investment agreement.
Both sides see it as a means to bolster an already strong relationship while boosting economic growth and creating jobs.
But the ambitious proposal has raised an array of concerns among citizens and politicians on both sides, including over aggressive deregulation, notably in the agriculture sector, and potentially weaker consumer protections.
On Tuesday, campaigners handed the EU a petition signed by more than 1.1 million people against the planned deal.