A Brexit deal must be signed by "November at the latest", the EU's chief negotiator has warned.
Michel Barnier told a press conference in Brussels there will be no agreement unless an operational "backstop" arrangement for the Irish Border can be agreed.
In the event of a hard no-deal Brexit, the EU wants a backstop that would effectively create a border down the Irish Sea between the island of Ireland and Great Britain.
But he said was “determined” to reach an agreement ahead of the October deadline, though he said there would be “flexibility” for further negotiations.
Standing alongside UK Brexit secretary Dominic Raab, he said: "Week after week and step by step we are eliminating subjects, bones of contention... I'm determined, we're going to find an agreement for an orderly withdrawal which is much better than the opposite and Dominic and I think it's possible to reach that in October."
Mr Barnier added: "If you take account of the date chosen by the United Kingdom to leave, that's March 29 which is in UK law and you simply count backwards the time that you need for ratification about three months here or there then it takes you to November at the latest. "It's as simple as that."
It follows concerns that a deal may fail to materialise before the deadline.
Mr Raab said that he wanted to continue “accelerating and intensifying” negotiations, adding: “We’re committed to resolving the deal by (the October council) and ultimately on my side I am stubbornly optimistic that a deal is within our reach.”
Earlier, Mr Barnier said a backstop is “essential to conclude the negotiations”, stating: “With no backstop there will be no agreement.” He described the issue as a “matter of some urgency”, adding that he had asked the Brexit Secretary to provide data on how the “necessary controls and checks take place”.
British prime minister Theresa May has repeatedly said she will refuse to contemplate any backstop deal that treats Northern Ireland differently from the rest of the UK.
The UK Government insists that any backstop position should include the UK as a whole. Mr Raab said the government “remained committed” to finding a solution in Northern Ireland.
He said: “On Northern Ireland we remain committed to giving effect to the joint report, continuing the work on the potential solutions, working with Michel and his team on some of the issues he’s raised and continuing to drive that forward.
“The solutions must be workable, they’ve got to be workable for the communities living in Northern Ireland and living in the Republic of Ireland.”
Mr Barnier also told media in Brussels that the future partnership between the EU and UK would be without precedent. He said: “If we achieve what was in the March guidelines then you really do have a partnership with no precedent, this a very ambitious free trade agreement, specific agreements in all sorts of area of common interest.”
Mr Barnier was later asked if he believed the Conservative Party Conference would have an impact on negotiations, he said: “I’m not going to comment on the internal political life on the UK, conferences of this party or that party. “We’re negotiating with Theresa May’s Government with Dominic Raab and his team and they’re the ones round the negotiating table.” –PA