EU President Donald Tusk warned Thursday after talks with Prime Minister Theresa May that Britain's plan for post-Brexit trade arrangements simply "will not work".
After two days of talks in the Austrian city of Salzburg, Tusk told reporters that European Union leaders believe May's so-called Chequers plan for Brexit would undermine the bloc's single market.
The Polish former leader said the atmosphere in the talks between May and the other 27 leaders had been better than before but that stark differences remained on trade and the question of the Irish border.
"It must be clear that there are some issues where we are not ready to compromise. Firstly, of the four fundamental freedoms, the single market -- this is why we remain sceptical of Chequers," Tusk said.
"The Irish question remains our priority too and for this, we need only goodwill -- which we feel, the atmosphere was better than two or three weeks ago -- but the Irish question needs something more than good intentions," Tusk said.
"We need tough, clear and precise guarantees. This is why we need more time, but we hope to be ready in October," he said, dubbing the planned October 18 EU summit the "moment of truth".
Both Tusk and summit host Austrian Chancellor Sebastian Kurz said a follow-on November emergency summit would only go ahead if enough progress is made by October to justify it.