The European Union is the UK's biggest trading partner, taking 44% of all British exports and supplying 53% of its imports. If Britain fails to strike a trade deal with the EU, it will have to adopt World Trade Organization rules -- known as "most favored nation status" -- which would see the imposition of billions of euros in tariffs on imports and exports between the EU and UK. However, British trade officials are discreetly exploring plan B with the Geneva-based WTO: an interim "zero-for-zero" tariff deal for up to 10 years, allowing more time for a full trade agreement to be negotiated. POLITICO, a political journalism website, reports that under a little-known WTO clause, the UK and Brussels would be allowed a "reasonable length of time" after Brexit to agree on a free-trade deal. The provision is set out in Article 24, paragraph 5(c) of the General Agreement on Tariffs and Trade. A Geneva-based official who spoke to POLITICO on condition of anonymity said the idea for a 10-year deal that set tariffs at zero was gaining ground. "What's important for you to take away is there is not a great swell of bitterness towards the British in Geneva," the official said. "The attitude is nothing like what it is in Brussels." The official added that an interim agreement that allowed existing tariff-free trade to continue is likely to be accepted by the "vast majority" of WTO members.