BRUSSELS — The European Union will make no new offer on Brexit and those who promoted Britain's exit without any understanding of how to deliver it deserve a "special place in hell", EU Council President Donald Tusk said on Wednesday.

The United Kingdom is on course to leave the European Union on March 29 without a deal unless Prime Minister Theresa May can convince the bloc to reopen the divorce deal she agreed in November and then sell it to skeptical British lawmakers.

As companies and governments across Europe step up preparations for the turmoil of a no-deal exit, diplomats and officials said the United Kingdom now faces three main options: a no-deal exit, a last-minute deal or a delay to Brexit.

Rebuffing May's bid to renegotiate just a day before she is due in Brussels, Tusk said he had abandoned hope that Brexit might be stopped and said his priority was now to avert a "fiasco" when the UK leaves.

"I've been wondering what that special place in hell looks like, for those who promoted Brexit, without even a sketch of a plan how to carry it out safely," Tusk said at a joint news conference with Irish Prime Minister Leo Varadkar.

The remark angered Brexit supporters in Britain. Veteran Brexiteer Nigel Farage retorted: "After Brexit we will be free of unelected, arrogant bullies like you —sounds like heaven to me."

Pro-Brexit Conservative lawmaker Peter Bone said Tusk's comments were an outrageous insult to the British people.

While Tusk was clear the EU would not reopen the divorce deal, he also said he still believed that a common Brexit solution was possible.

Varadkar said the divorce deal, which was rejected by the UK parliament, was "the best possible". He said Britain's political instability further proved the need for a "backstop" insurance policy — the main obstacle to a deal — to keep the border between Ireland and UK-ruled Northern Ireland open after Brexit.

In a stark indication of the stakes for the United Kingdom of a disorderly Brexit, Irish nationalists warned May to her face on Wednesday that if she allowed a no-deal Brexit then there would have to be a referendum on Irish unity.

"In the event of a crash... she must as a democrat return to the Good Friday Agreement and she must begin preparation for a referendum on Irish unity," Sinn Fein leader Mary Lou McDonald said, referring to the peace accord signed in 1998 that ended three decades of sectarian violence in Northern Ireland.

"Ireland will not be the collateral damage of the Tory Brexit," she added. Tory is another name for May's Conservative Party.

The United Kingdom's decision to leave the EU has strained ties between its constituent parts: England and Wales voted to leave the EU in the 2016 referendum while Scotland and Northern Ireland voted to stay.

At her meetings in Belfast, May tried to tackle the 'backstop', the main hurdle to a Brexit deal. May said she would seek an alternative arrangement, which avoids the need for a hard border, or legally binding changes to the border backstop to introduce a time limit or create an exit mechanism.

Brexit has snagged on the 310-mile (500-km) frontier because there is disagreement on how to monitor trade without physical checks on the border, which was marked by military checkpoints before the 1998 Good Friday peace agreement.

Under the divorce deal, the 'backstop' would come into effect if the two sides failed to come up with a better idea to keep the border open. It would mean the United Kingdom remaining bound by EU market and customs rules so that goods would not have to be checked.

But the Northern Irish party which props up May's government says it could endanger the province's place in the United Kingdom, while Brexit supporters in May's Conservative Party worry it would lock the country into EU rules for the long term.

British ministers, The Sun newspaper said, have been examining a plan drawn up by Japan's Fujitsu to track trade across the border, while the Telegraph said ministers had discussed delaying Brexit by eight weeks.

EU officials are asking May to embrace a proposal by the opposition Labour Party to join a permanent customs union with the bloc.

Such a move would remove the need for the backstop and, some in the EU believe, could produce a majority in the House of Commons for the defeated deal. But officials have low expectations ahead of her visit to Brussels on Thursday.

"Theresa May is not delivering on what she agreed with us," a senior EU diplomat said. "Her inability to build a cross-party agreement is staggering." — Reuters