The US wants Europe to scrap environmental legislation in the transatlantic trade talks and allow corporate lobbying to take precedence in decision-making, German media reported citing leaked negotiating documents.
"These leaked documents confirm what we have been saying for a long time, TTIP [Transatlantic Trade and Investment Partnership] would put corporations at the centre of policy-making, to the detriment of environment and public health."
The environmental group has identified this as the main concern, saying it would undermine a 70-year-old rule, which allows countries to restrict trade "to protect human, animal and plant life or health", or for "the conservation of exhaustible natural resources."
Washington is coaxing the European Union to open its vast market for environmentally risky US farm produce by threatening to block the US market for European car exports, thereby jeopardising a transatlantic free trade deal, German media quoted Greenpeace sources as saying.
The German media also said the documents disclosed by Greenpeace showed that the US was blocking an EU demand that arbitration of corporate disputes must be handled by public institutions as Washington wants them not to be made public.
The head of Germany's consumer advisory bureaus Klaus Müller told German newspaper Süddeutsche Zeitung that the texts confirmed "pretty much all of our fears in terms of what the US-Americans want to achieve on the food produce market through TTIP."
Greenpeace trade expert Jürgen Knirsch said what had so far trickled out of the talks had "sounded like a nightmare."
"Now we know that this could very much become reality," said Knirsch.
Germany, which is already reeling under an ongoing US probe into Volkswagen's cheating on emission norms, could be the biggest loser if US blocks auto exports from European Union.
German media, including the Süddeutsche Zeitung newspaper and two German public television channels, say 240 pages of text from secret transatlantic free trade talks obtained by Greenpeace show that the US is pressuring the EU.
Greenpeace is expected to publish the material related to the extremely secret US-EU negotiations on the proposed Transatlantic Trade and Investment Partnership (TTIP) during the past three years, later today.
Most Germans are opposed to the TTIP and the US is not happy with the huge economic surplus that Germany and China gain at its expense.
In fact, thousands of anti-TTIP activists demonstrated on the eve of US President Barack Obama's visit to a major Hanover trade exhibition last week.
The reports say by citing consumer safety to block auto exports from the EU, Washington wants EU to relax its consumer safety norms for US food products.
German news agency DPA said persons close to the talks had confirmed the authenticity of the documents.
Washington wanted the EU to replace its precautionary consumer safety principle with the liberal US approach of permitting foodstuffs until risks are proven, said the media outlets, including the ARD network's channels NDR and WDR.
The EU rules mandate that goods must first be certified as safe before importing them into its markets, which is likely to constrain imports of American gene-manipulated and hormone-treated produce.
Visiting Hanover last week, US President Barack Obama together with German Chancellor Angela Merkel called for urgency at the TTIP negotiations.
Obama also wants the talks to be concluded in 2017, beyond the next US presidential election due in November this year.