Washington and Brussels are scrambling to rescue the besieged TTIP trade deal, as it falters amid growing opposition from protest movements and politicians on both sides of the Atlantic.

Jean-Claude Juncker, president of the European Commission, travelled to Paris to sell the Transatlantic Trade and Investment Partnership to a convention of France's mayors.

He claimed TTIP would not undermine their interests.

“I believe that TTIP negotiations can yield a deal that will profit the European economy . . . without harming standards,” he said.

Despite opposition from Germany’s influential socialists and the French government, Mr Juncker has called for the 28 member states to reconfirm their commitment to the deal at a summit in June.

Michael Froman, US president Barack Obama’s trade tsar, warned that there was no “Plan B” if talks were not concluded this year.

TTIP’s supporters have also been blindsided by increasing opposition in the US, where Hillary Clinton, facing a challenge from the left, has abandoned her support for a similar Pacific trade pact, and Donald Trump has built his campaign around an anti-trade message.

With the clock running out on Mr Obama’s presidency, officials on both sides now believe the window is closing for a deal to be reached and approved in legislatures in Europe and the US.