Theresa May will say it is now up to the EU to prevent a hard border in Ireland after Brexit, telling affected residents she has “done that work” with her Chequers plan.

Speaking in Belfast, the prime minister will seek to calm fears about the impact of withdrawal on the province, by pledging to deliver a deal that “works for the whole UK, including Northern Ireland”.

She will describe the return of border posts and checks as “almost inconceivable” – arguing her proposals for a free trade area for goods can provide the solution.

But, in tough talk, Ms May will rule out further compromise, insisting it is “now for the EU to respond” and not to “fall back onto previous positions which have already been proven unworkable”.

“The government has done that work. The white paper is our plan for the future. It is the way to the stronger and brighter tomorrow that I know awaits the whole United Kingdom,” she will say.

The message will be delivered after Michel Barnier, the EU’s Brexit negotiator, again pointed to the need to agree a “backstop for Ireland” as a “matter of urgency”.

It will also come just hours before Mr Barnier is due to deliver the EU’s verdict on the Chequers plan, after a meeting of ministers from the bloc’s 27 other member states.

Even as she arrived for her first visit to the Irish border since the Brexit referendum two years ago, the prime minister faced criticism her plan was “too little, too late”.

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

Michelle O’Neill, Sinn Fein’s vice-president, said the British PM would learn about the “catastrophic implications” of Brexit and hear the “fear and trepidation” of people living and working near what will become the UK’s only land border with the EU.

The issue remains the biggest hurdle in the way of a Brexit deal – with the EU insisting it must be settled before it will discuss future trading arrangements.

On Wednesday, Ms May ducked a question about whether a “no deal” Brexit – which she says she will accept if necessary – would trigger a hard border, telling MPs: “There isn’t a sort of simple answer to that.”

In Belfast she will insist it would “not be acceptable” for people who cross the border every day – or for businesses with supply and distribution chains – for checks to return.

And she will insist the Chequers proposals can resolve the controversy through a “close future partnership between the UK and the EU”.

The proposed free trade area on goods would avoid the need for customs and regulatory checks, “meeting our firm commitments in respect of Northern Ireland”, she will say.

“For all of us who care about our country, for all of us who want this union of nations to thrive, that duty goes to the heart of what it means to be a United Kingdom, and what it means to be a government,” Ms May will say.

Urging the EU to “evolve their position in kind”, she will add: “On that basis, I look forward to resuming constructive discussions.”