As if British Prime Minister Theresa May wasn't facing enough pressure at home, the European Union piled on more Friday by insisting there must be real progress in the Brexit talks in the next two weeks if Britain wants negotiations to move on to future trade relations next month. After another inconclusive negotiating session, both sides said differences remained on vital divorce issues, including Britain's Brexit bill, the Irish border and the rights of citizens affected by Brexit. EU leaders are due to assess at a Dec. 14-15 summit whether "sufficient progress" has been made on divorce terms to move to Phase 2 of the talks, as Britain desires. EU chief negotiator Michel Barnier confirmed that means Britain needs to make a shift within two weeks to give the 27 other EU leaders time to assess things before their December meeting. European Commission Brexit chief negotiator Michel Barnier says Britain must clarify key issues in the divorce talks within two weeks if it wants negotiations to move on to future trade relations next month. (Charles McQuillan/Getty Images) The biggest stumbling bloc remains money. Britain has said it will pay to settle commitments it has made to the EU budget, but has not agreed to the EU's estimated bill of some 60 billion euros ($88.8 billion Cdn). Barnier said it was "imperative" to turn into concrete commitments May's promise that Britain will pay its financial dues before leaving the EU in March 2019. On Friday, May said the exit date will be included on the EU Withdrawal Bill that has passed its second reading in Parliament. Departure date and time "I have today set out the date and time of our exit from the European Union —11 p.m., 29th March 2019," she said in announcing she would amend the bill to enshrine those details — as a protection against delay. In a recognition that progress has been slow, U.K. Brexit Secretary David Davis said that "we need to see flexibility, imagination and willingness to make progress on both sides if these negotiations are to succeed." In Berlin, Steffen Seibert, spokesman for Chancellor Angela Merkel said Friday that "it is indeed in Great Britain's hands to create the conditions that would