EU and US negotiators ended a sixth round of trade liberalisation talks on Friday by vowing to maintain transparency, as anti-globalisation protesters nearby urged the project be scrapped.
"We have had intense discussions" that have been extremely technical so that "political decisions can be taken later," said chief European Union negotiator Ignacio Garcia Bercero at the end of the five-day talks in Brussels.
"A lot has changed since we started the talks a year ago," said chief US negotiator Dan Mullaney, adding that negotiators had spent "a great deal of time on regulatory issues".
Resistance in both the United States and the European Union has grown since the talks began a year ago, with activists worried that the deal is being negotiated behind close doors to the benefit of corporate interests.
"Show us the text!" a few dozen protestors from leftist and environmental groups shouted outside the European Commission headquarters, the Brussels building where the talks took place.
At the heart of their concerns is a proposal to create an investor-state dispute settlement mechanism, or ISDS -- an independent panel where companies could resolve regulatory disputes directly with foreign governments in the courts.
Activists and many members of European Parliament worry this would favour corporate interests at the expense of US and European consumers.
They are also suspicious that US demands for access to the EU food market will result in compromises on health and safety standards, allowing in for example US beef containing growth hormones.
The chief negotiators were adamant that the TTIP, as the Transatlantic Trade and Investment Partnership is known, would protect consumers.
"Nothing will be done that will endanger the protection of the environment, of health, of safety or indeed any other public policy objective in the US or EU," Bercio said.
The spying revelations by former security contractor Edward Snowden, which have heightened worries of privacy violations by US Internet and telecommunications giants, have especially driven popular EU resentment against the TTIP.
"Considering the NSA spying scandal, there is no basis for a trade agreement if the US does not commit to protecting the data of European citizens or economic operators," said Helmut Scholz, of the leftist parliamentary group GUE.
Officials have stressed that the primary objective of the TTIP is to reduce barriers and costs that arise from unnecessary regulation and differences in industrial standards.
"Opportunities for a major upgrade of one's biggest economic relationship do not come along often and we cannot afford to squander this one," US Trade Representative Michael Froman said in a statement from Washington.