Britain and the European Union hammered out a historic deal on Brexit divorce terms on Friday that allows them to move on to the all-important issue of the future relationship after the split. Prime Minister Theresa May rushed to Brussels for early morning talks with European Commission President Jean-Claude Juncker to reach the breakthrough. The European Commission announced that it "recommends sufficient progress" had been made by Britain on separation issues including the Irish border, Britains divorce bill, and citizens rights. But EU President Donald Tusk -- who will recommend to leaders at a summit next week to open trade and transition talks -- warned that the toughest task was to come. "Let us remember that the most difficult challenge is still ahead. We all know that breaking up is hard but breaking up and building a new relation is much harder," Tusk said. Negotiators worked through the night to seal an agreement after the EU set a deadline of Sunday. The Brexit divorce bill of between 35 and 39 billion pounds represents a fair settlement, a spokesman for May said. "We expect the range to be between 35 and 39 billion pounds," the spokesman said. "We would look at it as a fair settlement of our obligations." Nigel Farage, who led the drive to leave the EU as chairman of the UK Independence Party, said May had caved on critical points. Farage tweeted that the deal was "good news for Mrs. May as we can now move on to the next stage of humiliation." On the other side, anti-Brexit London Mayor Sadiq Khan said it is "extremely disappointing" that Britain is pledging to leave the single market and customs union. "Despite the progress today, it looks increasingly unlikely that we will get a deal that works in Londons best interests and protects jobs and growth across Britain," he said. Britain committed once again in the agreement to leave the EU on March 29, 2019. Negotiations must be wrapped up within a year to leave time for parliaments to endorse any deal.