Prime Minister Theresa May is expected to pile the pressure on Brussels on Friday, saying their willingness to budge could determine whether British MPs finally back a Brexit deal next week.

May is expected to say the European Union had some choices to make if it wanted to secure a withdrawal agreement and see Britain leave the bloc in an orderly fashion on March 29.

Talks between British and EU officials to break the Brexit deadlock are set to last into the weekend, ahead of a crucial parliamentary vote in London on Tuesday on whether MPs will accept the deal.

With just three weeks to go until the scheduled departure date of March 29, concern is growing about the possibility of Britain crashing out of the bloc after 46 years of membership with no deal in place.

British MPs have so far rejected the withdrawal agreement struck between London and Brussels, chiefly due to concerns over it’s “backstop” solution.

Talks since have focused on the “backstop”, which is designed to keep the Irish border open but which critics say could indefinitely lock Britain into a customs union with the EU.

May was to address an audience of workers in Grimsby, the North Sea port that is home to one of Britain’s biggest fishing fleets.

May will say that the government remains determined to secure legally binding changes to the backstop in advance of Tuesday’s vote on the withdrawal agreement.

“Just as MPs will face a big choice next week, the EU has to make a choice too,” May will say, according to her Downing Street office.

“We are both participants in this process. It is in the European interest for the UK to leave with a deal. 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.”

Grimsby ran the world’s largest fishing fleet by the mid-20th century but its prosperity dramatically declined after Britain joined the European communities and signed up to the Common Fisheries Policy.

Some 70% in the local North East Lincolnshire area voted in favour of Britain leaving the EU in the 2016 referendum.