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

Sigmar Gabriel of Germany, the EU's biggest economy, said on Sunday that negotiations over the Transatlantic Trade and Investment Partnership (TTIP) had failed because Europe rejected some U.S. demands.

Asked to comment on 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.

The White House also disputed Gabriel's contention, saying it was still aiming to reach a deal by the end of the year. "It's going to require the resolution of some pretty thorny negotiations, but the president and his team are committed to doing that," White House spokesman Josh Earnest told reporters in Washington.

In Berlin, Germany's leading industry associations were critical of Gabriel's remarks and urged the German government to show greater commitment to free trade deals.

The head of industry association BDI, Ulrich Grillo, said it was "astonishing" that Gabriel, who is also vice chancellor and head of the co-governing Social Democrats, had declared the TTIP talks a failure when negotiations were still going on.

Top officials of other industry associations such as VDMA and the Auto Industry Association VDA also spoke out against Gabriel's comments, which highlighted growing divisions within Chancellor Angela Merkel's ruling coalition ahead of next year's elections.

Three years of negotiations have 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 U.S.-EU free trade deal see it bringing economic gains on both sides of the Atlantic. EU trade ministers will discuss the issue in Bratislava on Sept. 22.

Schinas said the Commission was still ready to finalize 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".

Commenting separately on Gabriel's remarks, Lithuanian Foreign Minister Linas Linkevicius said he believed arriving at a deal would benefit both the EU and the United States.

"It would be better for all sides to agree," he said. "Of course, not at an expense of our interests. We have to defend our interests, but we also have to negotiate and conclude this agreement. It would be a big boost for economies, jobs, trade."

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

(Reporting by Gabriela Baczynska; Additional reporting by Michael Nienaber in Berlin, Nerijus Adomaitis in Oslo and Tim Ahmann in Washington; Editing by Peter Cooney)