The European Commission has suspended talks on part of a far-reaching EU-US free trade deal amid concern that hard-won social protections in Europe might be undermined.
The trade negotiations began last year but now the Commission has launched a three-month public consultation on the proposed investment rules for firms.
The aim is to close legal loopholes.
Consumer and environmental lobbyists say there is a risk of the EU accepting lower US standards in many areas.
The proposed EU-US Transatlantic Trade and Investment Partnership (TTIP) could bring huge benefits for Europe and America, the Commission says.