A new proposal that would see a temporary economic arrangement to avoid a hard border between Ireland and Northern Ireland was "unclear," the European Union's chief negotiator Michel Barnier said on Friday.

Britain proposed a compromise solution for the Irish border issue on Thursday — a so-called 'backstop' proposal — for a temporary customs arrangement that would keep Northern Ireland inside the EU's single market in goods for a temporary period.

London said the backstop would only be a last resort and would end by December 2021.

Read more: Brexit: Theresa May calls for unprecedented UK-EU economic partnership

Britain's proposal to keep goods and services flowing between its territory of Northern Ireland and EU member Ireland "raises more questions than it provides answers," Barnier said.

Barnier said the UK's proposal for keeping open its border with Ireland after it leaves the bloc in 2019 also appeared to be geared toward extending it to the whole of Britain — something Barnier said could not be done.

"Let me be very clear. Our backstop cannot be extended to the whole UK. Why? Because it has been designed for the specific situation of Northern Ireland," he said. "What does it do? Northern Ireland would form part of our customs territory. What is feasible for a territory the size of Northern Ireland is not necessarily feasible for the whole UK."

He said some progress had been made in talks and that a June 28 summit on Brexit could see a breakthrough. But he also called the UK's approach to trade "fairly paradoxical" and said much work was needed before agreeing the terms of its exit from the bloc, set for March 2019.

"UK ministers seem nostalgic for EU membership, wanting all the benefits without being bound by the rules," he said, adding that London needed to respect its own red lines in the Brexit talks.

Timing is of the essence

Britain is set to leave the EU at the end of March, but an agreement on its withdrawal must be found by October to give EU parliaments time to ratify it.

"We are today at a time of decisions and choices. Time is running out. In less than 10 months the UK is leaving the European Union as it has wanted," Barnier said.

Not intimidated

Barnier said the EU would not be intimidated by London in the Brexit negotiations. "We are not going to be intimidated by this form of blame game," Barnier told a press conference, urging "more realism" from Britain about what can be achieved.

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jbh/kms (Reuters, AFP, AP)