European Council President Donald Tusk attends a press conference following a special meeting of the European Council to endorse the draft Brexit withdrawal agreement and to approve the draft political declaration on future EU-UK relations on November 25, 2018 in Brussels. - The European Union's top official urged British lawmakers to ratify the Brexit deal Prime Minister Theresa May has negotiated with European leaders, warning it will not be modified. "This is the best deal possible for Britain, this is the best deal possible for Europe. This is the only deal possible," Jean-Claude Juncker, the president of the European Commission, said after a Brussels summit. (Photo by JOHN THYS / AFP) (Photo credit should read JOHN THYS/AFP/Getty Images)