Prime Minister Theresa May’s government accepts a Brexit deal will need to be struck in less than 15 months of talks if the U.K. is to avoid tumbling out of the European Union before establishing new ties with the bloc, a British official said. While the EU’s Lisbon Treaty allows for two years of discussions once Britain formally requests a divorce, both sides are facing up to the likelihood of a shorter time frame, given that the final accord will need to be approved by the European Parliament. The probable intensity and complexity of the debate leaves the U.K. pushing the EU to allow for different parts of the split to be addressed simultaneously, said the official, who was speaking on condition of anonymity because the details of the government’s plans are private. The terms of the withdrawal would thus be discussed in parallel with the details of the future relationship. Such an approach would stand in contrast to the three-tier strategy preferred by the 27 other members of the EU. Under that scenario, the U.K. would first need to agree on a departure payment and then settle border arrangements before it could start hammering out its longer-term links to the rest of the bloc. Cliff Edge Failure to determine a post-Brexit future before the U.K. leaves the EU would risk it having no trading or legal arrangement with its biggest market, a scenario already unnerving companies that are lobbying May to avoid such a “cliff edge.” Banks are among those warning that a continued lack of clarity will soon force them to begin shifting jobs and operations overseas. Getting a sign-off from the EU parliament may prove the biggest hurdle, given that many of its 751 members could seek to block the Brexit accord, the U.K. official acknowledged. The EU holds elections to the legislature in May 2019, so governments will also want time to focus on those rather than the U.K.’s departure. With May still saying she will invoke Article 50 of the Lisbon Treaty by the end of March, officials across Europe appeared this week to harden their attitude toward the pending negotiations. German Chancellor Angela Merkel and EU President Donald Tusk rejected an overture from British lawmakers to swiftly agree to guarantee reciprocal rights for EU and U.K. citizens after Brexit. ‘Give Reassurances’ May told the House of Commons on Wednesday that she wants to “give reassurances” to the 3 million people from other EU countries living in the U.K. and about 1.2 million Britons resident elsewhere in the bloc. Merkel said on Tuesday there can be no side-deals or informal planning before May acts on Article 50, a point echoed this week by officials from the European Commission, Italy and Malta. Meantime, Luxembourg Prime Minister Xavier Bettel said he would be against allowing Britain a transitional agreement that some have suggested could bridge any gap between leaving the EU and establishing new trading terms. “What would interim mean?” Bettel told Agence France-Presse in an interview published on Tuesday. “That we are going to make a hybrid status now? Either you’re a member or you’re not a member of the European Union. There is no in-between status, there is no hybrid status.” There are other complications to the Brexit timetable. Britain’s Supreme Court will consider next week whether May or Parliament has the power to invoke Article 50. Even when it is triggered, European officials may wait the outcome of elections in France and Germany next year to fully engage with the U.K., further reducing the scope for talks. The British premier is also coming under pressure at home. Buffer Period Bank of England Governor Mark Carney publicly said for the first time on Wednesday that he would back a buffer period after Brexit, noting that all trade deals and financial reforms need a transition time. London Mayor Sadiq Khan also used a speech to again propose London-only visas if the government is unable to safeguard the capital’s access to foreign skills. Nearly one in seven London workers were born elsewhere in the EU. Meantime, Peter Bone, a pro-Brexit member of May’s Conservative Party, introduced a bill to Parliament to force the prime minister to deliver on her pledge to deliver Article 50 in the first quarter of next year. The proposal seeks to legally compel May, who backed staying in the EU in the June referendum, to stick to the deadline.