With a deadline looming ever more menacingly, the European Union’s chief negotiator on the post-Brexit trade deal with Britain on Wednesday publicly blamed London for a lack of progress in the two sides’ belated attempt to reach an even rudimentary agreement. “At this stage, there are still too many difficulties remaining on important topics,” Michel Barnier said on his way to brief the envoys of the 27 member states. In a Twitter comment later, Barnier said, “Despite EU efforts to find solutions, very serious divergences remain.” Britain’s chief negotiator, David Frost, said he agreed that “wide divergences remain on some key issues.” “We continue to work to find solutions that fully respect U.K. sovereignty,” Frost tweeted. Barnier’s comments threw a dampener on optimistic reports that p...