Ireland’s prime minister has said he expects a Brexit deal on the Northern Irish border “in the next couple of weeks”.

Speaking at a meeting of British and Irish officials on the Isle of Man, Leo Varadkar warned, however, that a deal was still “not guaranteed”.

It comes after a leaked letter from Theresa May to Northern Irish unionists in the DUP warned that plans for a border down the Irish sea could be included in the withdrawal agreement.

Addressing reporters at the British-Irish Council, Mr Varadkar said: “In terms of the backstop what’s envisaged is that it would be there as a protocol to the withdrawal agreement.

“But I think when we talk about the backstop we should always recall what the objective is and the most important thing for me is the objective – to give everyone in Northern Ireland and Ireland the assurance that a hard border will not develop between Northern and South no matter what else might happen in the year ahead.

“That is why we’re seeking one that is legally operative and one that gives us that guarantee that is necessary. I think we are at a sensitive point in the negotiations. A successful outcome is not guaranteed, but I think it is possible in the next couple of weeks and probably with that in mind the less said the better about the detail of that.”

Despite the contents of Friday’s leaked letter, David Lidington, the cabinet minister attending the summit in Douglas for the UK, said Britain would not accept “carving out” Northern Ireland from the rest of the nation.

Cabinet minister David Lidington says the UK would not agree to dividing Northern Ireland from Great Britain (PA) (PA Wire/PA Images)

“On the commitments that were made in the joint report of December 2017 and all the various commitments that were made in that report – the prime minister’s always been very clear, that we won’t accept something that involves sort of carving out Northern Ireland from the rest of the United Kingdom,” he said.

The dispute centres around the Irish backstop, a legal mechanism to prevent a hard border from arising on the island of Ireland in order to preserve the Good Friday Agreement.

Brexit threatens life on the Irish border: in pictures Show all 15 1 /15 Brexit threatens life on the Irish border: in pictures Brexit threatens life on the Irish border: in pictures An abandoned shop is seen in Mullan, Co Monaghan. The building was home to four families who left during the Troubles. The town was largely abandoned after the hard border was put in place during the conflict. Mullan has seen some regeneration in recent years, but faces an uncertain future with Brexit on the horizon Reuters Brexit threatens life on the Irish border: in pictures A defaced ‘Welcome to Northern Ireland’ sign stands on the border in Middletown, Co Armagh Reuters Brexit threatens life on the Irish border: in pictures Mervyn Johnson owns a garage in the border town of Pettigo, which straddles the counties of Donegal and Fermanagh. ‘I’ve been here since 1956, it was a bit of a problem for a few years. My premises has been blown up about six or seven times, we just kept building and starting again,’ Johnson said laughing. ‘We just got used to it [the hard border] really but now that it’s gone, we wouldn't like it back again’ Reuters Brexit threatens life on the Irish border: in pictures Farmer Gordon Crockett’s Coshquin farm straddles both Derry/Londonderry in the North and Donegal in the Republic. ‘At the minute there is no real problem, you can cross the border as free as you want. We could cross it six or eight times a day,’ said Crockett. ‘If there was any sort of obstruction it would slow down our work every day’ Reuters Brexit threatens life on the Irish border: in pictures John Murphy flies the European flag outside his home near the border village of Forkhill, Co Armagh Reuters Brexit threatens life on the Irish border: in pictures Potter Brenda McGinn stands outside her Mullan, Co Monaghan, studio – the former Jas Boylan shoe factory which was the main employer in the area until it shut down due to the Troubles. ‘When I came back, this would have been somewhere you would have driven through and have been quite sad. It was a decrepit looking village,’ said McGinn, whose Busy Bee Ceramics is one of a handful of enterprises restoring life to the community. ‘Now this is a revitalised, old hidden village’ Reuters Brexit threatens life on the Irish border: in pictures Union Flag colours painted on kerbstones and bus-stops along the border village of Newbuildings, Co Derry/Londonderry Reuters Brexit threatens life on the Irish border: in pictures Grass reflected in Lattone Lough, which is split by the border between Cavan and Fermanagh, seen from near Ballinacor, Northern Ireland Reuters Brexit threatens life on the Irish border: in pictures Donegalman David McClintock sits in the Border Cafe in the village of Muff, which straddles Donegal and Derry/Londonderry Reuters Brexit threatens life on the Irish border: in pictures An old Irish phone box stands alongside a bus stop in the border town of Glaslough, Co Monaghan Reuters Brexit threatens life on the Irish border: in pictures Billboards are viewed from inside a disused customs hut in Carrickcarnon, Co Down, on the border with Co Louth in the Republic Reuters Brexit threatens life on the Irish border: in pictures Seamus McQuaid takes packages that locals on the Irish side of the border have delivered to his business, McQuaid Auto-Parts, to save money on postal fees, near the Co Fermanagh village of Newtownbutler. ‘I live in the south but the business is in the North,’ said McQaid. "I wholesale into the Republic of Ireland so if there’s duty, I’ll have to set up a company 200 yards up the road to sell to my customers. I’ll have to bring the same product in through Dublin instead of Belfast’ Reuters Brexit threatens life on the Irish border: in pictures A disused Great Northern Railway line and station that was for customs and excise on the border town of Glenfarne, Co Leitrim Reuters Brexit threatens life on the Irish border: in pictures Alice Mullen, from Monaghan in the Republic of Ireland, does her shopping at a former customs post on the border in Middletown, Co Armagh. ‘I’d be very worried if it was a hard border, I remember when people were divided. I would be very afraid of the threat to the peace process, it was a dreadful time to live through. Even to go to mass on a Sunday, you’d have to go through checkpoints. It is terribly stressful,’ said Mullen. ‘All those barricades and boundaries were pulled down. I see it as a huge big exercise of trust and I do believe everyone breathed a sigh of relief’ Reuters Brexit threatens life on the Irish border: in pictures A bus stop and red post box stand in the border town of Jonesborough, Co Armagh Reuters

The EU is insisting that the UK sign up to a policy that would keep Northern Ireland aligned to the EU’s single market and customs regulations, which could mean checks between Britain and Northern Ireland.

Ms May has long resisted the demand, but the leaked letter suggests she may now acquiesce – though she maintains it will never be used. The prime minister has also devised another backstop that would effectively keep the whole UK in a customs union with the EU if no future trade deal removes the need for it.