BRUSSELS/LONDON (Reuters) - Britain and European Union have just hours left to navigate the very narrow path to a trade deal that would prevent the most turbulent finale to the Brexit crisis in less than two weeks’ time, EU chief negotiator Michel Barnier said on Friday. As talks go down to the wire, both sides are demanding the other compromise amid a flurry of often conflicting messages that, variously, a deal is possible, a deal is in serious trouble or that a deal is imminent. An accord would ensure that the goods trade which makes up half of annual EU-UK commerce, worth nearly a trillion dollars in all, would remain free of tariffs and quotas beyond Dec. 31. “It’s the moment of truth,” Barnier told the European Parliament in Brussels. “There is a chance of getting an agreement but the path to such an agreement is very narrow.” “We find ourselves in a very serious and sombre situation,” Barnier said. “We have very little time remaining, just a few hours to work through these negotiations in a useful fashion if we want this agreement to enter into force on the first of January.” Sterling, which has oscillated to the beat of Brexit news for five years, fell 0.5% against the U.S. dollar to $1.3513, retracing most of Thursday’s gain. “SERIOUS SITUATION” British Prime Minister Boris Johnson told European Commission President Ursula von der Leyen in a call on Thursday that talks were in a “serious situation” and that it now looked very likely that an agreement would not be reached unless the EU position changed substantially. Von der Leyen said progress had been made but bridging the divide on some areas, especially fisheries, would be “very challenging”. While Barnier said the sides were striving at an agreement, he said the 27-nation bloc would not sign a deal that would undercut its cherished single market of 450 million consumers. He said the EU needed to be able to impose trade barriers should the UK change its regulations to offer substandard goods on the bloc’s market. For fisheries, he said the bloc also wanted to be free to retaliate by curbing EU market access to UK fish products should Britain squeeze European ships out of its waters. “That is where we get to one of the most difficult issues at the moment. Fisheries being part and parcel of the trade relationship,” said Barnier, adding he did not know if the talks would yield a deal, or not. “We have to be prepared for all eventualities.” Johnson, the face of the 2016 Brexit campaign, will ultimately have to decide whether to accept the narrow deal on offer from the EU or risk the economic chaos and domestic political applause that walking away would trigger. Britain joined the EU in 1973, and formally left on Jan. 31. Since then, it has been in a transition period under which rules on trade, travel and business remain unchanged. Failure to agree a deal on goods trade would send shockwaves through financial markets, hurt the economies of Europe, snarl borders and sow chaos along delicate supply chains that stretch across Europe and beyond. Senior British min