LONDON (AP) — Britain laid out its opening demands for the upcoming trade talks with the European Union on Thursday, including a blunt threat to walk away from the negotiating table if there is no progress within four months. The two sides appear headed for a rocky first round of negotiations as they try to forge a new relationship following the U.K.’s departure from the now 27-nation bloc. Britain and the EU both say they want to reach a free trade agreement, but have starkly divergent views on how it should be overseen and what constitutes fair competition between their two economies. The EU says Britain must agree to follow the bloc’s rules in areas ranging from state aid to environmental protections, and give European boats access to U.K.