Theresa May will urge the EU to help get her Brexit deal through the Commons by agreeing legally binding changes to the controversial backstop.
On Friday, she will say the EU’s actions will “have a big impact on the outcome” when MPs vote on it next week.
But Labour’s Sir Keir Starmer said it was now “clear” the PM “will not be able to deliver the changes she promised to her failed Brexit deal”.
The EU says the UK must come forward with new ideas to break the deadlock.
The UK is due to leave on 29 March.
Mrs May will visit workers in Grimsby, Lincolnshire, later, days before the second “meaningful vote” in the Commons on the withdrawal deal she has negotiated with the EU.
She will tell them: “Just as MPs will face a big choice next week, the EU has to make a choice too.
“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.”
BBC political correspondent Ben Wright said making a public appeal to the EU for compromise just four days before the vote was an admission of how tough negotiations with the EU were proving.
The first vote, in January, saw the deal rejected by 432 votes to 202, the largest defeat for a sitting government in history.
Mrs May is seeking legally-enforceable changes to the backstop – a controversial insurance policy designed to prevent physical checks on the border between Northern Ireland and the Republic of Ireland – but there have been few visible signs of progress.
Leading Brexiteers are looking for reassurances that the backstop – which would see the UK aligned with EU customs rules until the two sides’ future relationship is agreed or alternative arrangements worked out – will not endure indefinitely.
The European Commission said on Wednesday that “no solution has been identified” to the Irish backstop and it has refused to rewrite the withdrawal deal already struck, which is designed to ensure an orderly Brexit on 29 March and pave the way for trade talks.
But Foreign Secretary Jeremy Hunt told the BBC the UK’s demands were “not unreasonable” and it was “entirely possible” there would be a breakthrough in the next 72 hours.
He told BBC Radio 4’s Today that the other 27 EU members needed to be flexible if they were to get MPs onside and suggested the EU would be blamed “if this ends in acrimony”.
