BBC political editor Laura Kuenssberg said it was understood that the EU was prepared to accept the idea of the whole of the United Kingdom remaining in the customs union if a trade deal can not be done during the so-called "transition period", which is due to end in December 2020.
"But that's not a question for us, we're not members of the Conservative Party".
Barnier said Brexit would trigger the need for customs, Value-Added Tax and compliance checks with EU standards between Ireland and Northern Ireland in the event that a planned "backstop" were triggered because a future EU-UK trade deal was not sufficient in itself to ensure the land frontier was not a "hard border".
Britain's global trade, environment and Brexit ministers told Prime Minister Theresa May at a meeting on Thursday that they are concerned the whole of Britain could remain in the customs union for an open-ended period of time, the BBC said.
'Bin Salman ordered operation against Khashoggi'
He has been critical the monarchy's continued arrest of critics on both the left and right, despite its professed reforms. The issue threatened the strong relationship the Trump administration has constructed with Mohammed Bin Salman .
"An agreement is within reach if we are to end these negotiations on the 17 October at the European Council [summit]", Barnier told European entrepreneurs in the European Parliament.
But one of May's key allies in the Cabinet, finance minister Philip Hammond, sought to quell the prospect of an all-out rebellion and said there has been a "measurable change of pace" in talks with the European Union, adding to the sense of optimism that a deal could be imminent.
"And we are still open - we are still open - to the idea of having a customs union with the UK".
"The only visible systematic checks between Northern Ireland and the rest of the United Kingdom would involve scanning the bar codes on lorries or containers, which should be done on ferries or in transit ports".
The Irish government wants a 'backstop' which would effectively keep the north within the single market and prevent customs checks at the border in the event of a no deal Brexit.
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This growth exceeds that achieved in any of the years between 2012 and 2016, he said. But US growth will decline once parts of its fiscal stimulus go into reverse.
For industrial goods, he said checks could be done by "market surveillance authorities", and on-site in the companies.
Michel Barnier announced 80-85% of the treaty had been agreed and promised Brussels would respect the "constitutional integrity" of the UK.
Besides the Irish border issue, the key areas still to be negotiated are the geographical indications of products and the governance of the implementation of the deal.
Former Labour leader Tony Blair added his voice to calls to vote down any Brexit deal by May, hoping that would open the way for another referendum in which Britons would this time decide to stay, after their popular vote in June 2016 that resulted in a narrow "Leave" victory. "It will not, and it can not be business as usual", he said, adding that the European Commission has set up plans to help businesses. Barnier said the cost of such a development would be "very high" for Britain but also some sectors of the European Union economy, such as the auto industry. Then, EU leaders advisors are meeting on Monday in preparation for the summit.
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Saudi officials say the journalist left the consulate after his brief visit, rejecting the Turkish claims as baseless. Mr Trump told reporters he had talked to the Saudi authorities "at the highest level" about Mr Khashoggi .