Britain has been told it must 'rework' its proposals on the Irish border as the Brexit negotiations enter a "decisive phase".
European Council President Donald Tusk said he would call a summit of European Union leaders in mid-November in a bid to finalise a Brexit deal with Britain.
Speaking ahead of a gathering of EU leaders in the Austrian city of Salzburg, which is being attended by Taoiseach Leo Varadkar, Mr Tusk said: "The Brexit negotiations are entering their decisive phase.
"Various scenarios are still possible today, but I would like to stress that some of (British) Prime Minister May's proposals from Chequers indicate a positive evolution in the UK's approach as well as a will to minimise the negative effects of Brexit."
While noting that the UK was prepared to work closely with the EU on security and foreign policy post-Brexit, Mr Tusk said there still needs to be changes to Britain's approach - particularly on the future of the Irish border and economic cooperation.
"Among other things, the readiness to cooperate closely in the area of security and foreign policy. On other issues, such as the Irish question, or the framework for economic cooperation, the UK's proposals will need to be reworked and further negotiated.
"Today there is perhaps more hope, but there is surely less and less time.
"Therefore, every day that is left, we must use for talks."
"I would like to finalise them still this autumn."
Mr Tusk is proposing to call an additional summit around mid-November for this.
Earlier, the EU's chief Brexit negotiator, Michel Barnier, said he wanted to "de-dramatise" the border issue - suggesting the majority of checks on imports and exports could take place away from the border itself.
But the DUP, which props up Theresa May's government at Westminster, dismissed Mr Barnier's proposals.
Deputy leader Nigel Dodds said: "Despite the talk of improvements the backstop being insisted upon by the EU would mean a different regime for Northern Ireland compared to the rest of the UK.
"It still means a border down the Irish Sea although with different kinds of checks.
"The fact is that both Theresa May and the Labour Party have said no British prime minister could accept such a concept.
"It is not just unionists who object."
Tánaiste Simon Coveney met with Mr Barnier on Tuesday, and stressed that there will be no withdrawal deal without a "legally operable Irish backstop".
Additional reporting: IRN
