EU and UK in Brexit brinksmanship

"We are both participants in this process. It is in the European interest for the UK to leave with a deal," she planned to add.

"We are working with them, but the decisions that the European Union makes over the next few days will have a big impact on the outcome of the vote," she also aimed to say.

Her speech, in a town where 71 percent of people chose to leave in the referendum in 2016, comes as British MPs prepare to vote on the UK withdrawal agreement on Tuesday (12 March).

It was already rejected by a historic majority in January, among concern that the UK would have to stay in the EU customs union until it finds a way to avoid a hard border on the island of Ireland.

May's reference to "the decisions that the European Union makes" comes amid 11th-hour efforts by British negotiators for the EU to place a time-limit on the customs union deal.

But the EU has ruled that out and France said earlier this week it was waiting for the UK to make a credible proposal instead.

Some expect British attorney general Geoffrey Cox to come up with a legal fudge that would change little in substance but would give May a political alibi to say she had won concessions.

One option under consideration is an arbitration panel that would decide when the UK could walk away from the Irish deal in future.

If the MPs reject the EU withdrawal bill again, they are to get two subsequent votes, expected on Wednesday and Thursday.

Wednesday's vote would be on whether to reject outright a no-deal exit.

Thursday's one would be on whether to delay the Brexit date, either by a few months or for up to two years.

Unknown territory

Philip Hammond, Britain's pro-European finance minister, warned hardline Brexiteers in his and May's own Conservative party that if they rejected the deal on Tuesday, it would lead to "unknown territory where a consensus will have to be forged across the House of Commons and that will inevitably mean compromises being made" with anti-Brexit MPs in the opposition.

Liam Fox, the pro-Brexit trade minister, warned MPs that if there was a lengthy extension, it might mean no Brexit in the end.

"There will be a risk that we might not deliver Brexit at all," he told British broadcaster the BBC.

"In parliament, there is a large number of MPs who do not see it as their primary objective to deliver the referendum and would want to keep us locked in the EU," he added.

Meanwhile, Keir Starmer, the opposition Labour party's shadow Brexit minister, heaped scorn on the government's handling of the process.

"It's becoming increasingly clear that Theresa May will not be able to deliver the changes she promised to her failed Brexit deal. This speech [in Grimsby] looks set to be an admission of failure," he said on Thursday.

"After two years of negotiation, the government is simply incapable of delivering a Brexit deal that protects jobs, the economy, and people's livelihoods," Starmer said.

The two years since the referendum has seen the UK try to negotiate bilateral deals on trade, aviation, energy supplies, and other issues with non-EU states.

No-deal concerns

But just 43 out of the 161 international treaties said to be of key importance to the UK have been completed so far.

"If the UK leaves the EU without a deal, it will not be possible to complete the transition of all agreements by 29 March 2019," the British Brexit secretary, Stephen Barclay, said on Thursday.

The most basic rights - to let UK citizens keep on living in Europe and EU nationals to keep living in the UK - would also be up in the air if there was a no-deal exit.

The UK has said all EU citizens can apply for "settled status" in the UK no matter what happens.

But its commitment for EU citizens to keep their rights is part of the withdrawal deal that will most likely be rejected next week.

On the other side, each of the 27 EU states would have to decide individually what to do with its UK residents, among preparations by the Czech Republic and Poland to also let them stay no matter what.