BRUSSELS—The European Union won’t agree to any future trade pact with the U.K. until after Britain leaves the bloc and will look to set tight conditions on a divorce deal, according to a draft of the bloc’s negotiating guidelines.

European Council President Donald Tusk on Friday sent the guidelines, which must be agreed on at a summit of leaders from the remaining 27 member countries on April 29, to EU capitals.

They say the priority in exit talks will be on securing clear divorce terms and that discussions will give an “overall understanding” of the future relationship during the two-year negotiating period. They said there would be one divorce package for the U.K. and that there could be no bilateral side deals between the country and the other member states.

“The union and its member states stand ready to engage in preliminary and preparatory discussions to this end…as soon as sufficient progress has been made in the first phase towards reaching a satisfactory agreement on the arrangements for an orderly withdrawal,” the guidelines say.

U.K. Prime Minister Theresa May said on Wednesday when she launched Britain’s formal exit process that she wanted to reach an agreement on a future trade deal during the two years of exit talks.

The bloc insisted that the U.K. must settle an exit bill that includes all of the U.K.’s legal and financial commitments, including Britain’s continent liabilities as an EU member. They say that Britain must fully abide by EU law, which would include offering full rights and benefits to EU citizens who come to the U.K. before the exit talks wrap up in March 2019.

“In these negotiations the union will act as one. It will be constructive throughout and will strive to find an agreement,” the draft guidelines say.” But the bloc will prepare a contingency plan in case the negotiations fail.