The European Union's executive has said it has a unanimous mandate from the bloc's 28 members to finalise negotiations on a free trade deal with the United States, a day after Germany's economy minister said the talks had "de facto failed".

Economy Minister Sigmar Gabriel of Germany, the EU's biggest economy, said yesterday negotiations over the Transatlantic Trade and Investment Partnership (TTIP) had failed because Europe rejected some US demands.

Asked to comment on Mr Gabriel's remarks, a European Commission spokesman said "the ball is still rolling" on TTIP.

"Although trade talks take time, the ball is rolling right now and the Commission is making steady progress in the ongoing TTIP negotiations," Margaritis Schinas told a news conference.

"Talks are now indeed entering crucial stage as we have proposals for almost all chapters on the table and a good sense of the outline of the future agreement."

Three years of negotiations failed to resolve multiple differences, including over food and environmental safety, with critics saying the pact would hand too much power to big multinationals at the expense of consumers and workers.

Backers of a sweeping US-EU free trade deal see it bringing economic gains on both sides of the Atlantic. EU trade ministers will discuss the issue when they next meet in Bratislava on September 22.

Ms Schinas said the Commission was still ready to finalise the deal by the end of the year but not at the expense of "Europe's safety, health, social and data protection standards, or our cultural diversity".

Britain's June vote to leave the EU has further clouded the picture, though Ms Schinas insisted Brussels was still negotiating on behalf of all 28 members of the bloc, including London.

But the prospect of a Brexit has triggered fresh doubt that TTIP could be completed in the final months of US President Barack Obama's term, as well as over Britain's exact status in any deal as London ponders its future ties with the EU.