European Council President Donald Tusk says Britain's Brexit proposals on the Irish border need to be "reworked and further negotiated".
He was speaking ahead of a gathering of EU leaders in Austria, which'll be attended by Taoiseach Leo Varadkar.
Mr Tusk said Brexit negotiations are entering their "decisive phase".
While he said "various scenarios" are still possible, there need 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."
He's proposing to call an additional summit around mid-November to finalise a Brexit deal.