The European Union's chief Brexit negotiator Michel Barnier said he had a "constructive meeting" with his British counterpart Stephen Barclay on Friday as both sides scrambled to thrash out a deal that would see the UK potentially exit the bloc at the end of this month. 

The meeting follows on the heels of British Prime Minister Boris Johnson and Irish Taoiseach Leo Varadkar agreeing to a "pathway" to a possible agreement on Thursday.

Barnier said: "Brexit is like climbing a mountain. We need vigilance, determination and patience."

The EU said deliberations over an amicable divorce were back on track despite significant challenges, especially on the status of the invisible land border between Northern Ireland and the Republic of Ireland, an EU member state.

EU Council President Donald Tusk said he has "received promising signals" from Varadkar that a deal is still achievable.

Tusk was earlier planning to pull the plug on negotiations but decided against it after the recent spate of talks between the UK, Ireland and the EU.

He said: "There is no guarantee of success and the time is practically up."

"A no-deal Brexit will never be the choice of the EU", Tusk added.

EU leaders are meeting on 17-18 October in Brussels, where Johnson hopes to formalize the UK's departure from the 28-nation bloc on 31 October, more than three years after the nation's referendum on whether to leave.