The UK's proposal to keep away from a laborious Irish border "raises more questions than it answers", says the EU's chief Brexit negotiator Michel Barnier.
Theresa May got here up with the plan for a time-limited "backstop" if a commerce deal isn't in place by 2021.
Mr Barnier mentioned he would look at the proposal "objectively".
But he mentioned the EU's most well-liked possibility would work higher and the UK couldn't take an "a la carte" method to the EU single market.