LONDON (Reuters) - Prime Minister Theresa May put the onus on the European Union to make concessions over the thorny issue of the Irish backstop in Brexit talks, or risk Britain leaving the EU without a deal, which she said would be against EU interests.

Britain's Prime Minister Theresa May is seen outside of Downing Street in London, Britain, March 6, 2019. REUTERS/Toby Melville

The two sides are at an impasse over the so-called backstop aimed at ensuring that there is a frictionless border between Northern Ireland and Ireland - the only land frontier between the United Kingdom and the bloc.

May is seeking legally binding assurances that Britain will not be trapped permanently in the backstop in order to win support for her exit deal, which was defeated by a record margin in parliament in January.

MPs will vote again on the deal next week, and May will say on Friday that the EU that should give ground in discussions over the backstop before then to help the deal go through.

“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,” May will say in a speech in Grimsby, northern England, according to pre-released extracts.

“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.”

May’s top lawyer returned empty handed from negotiations in Brussels this week.

The European Union has told Britain to rework its Irish backstop proposal by Friday, but a British source said on Thursday that the Brexit impasse was unlikely to be broken before the weekend because the EU was not moving.

But foreign minister Jeremy Hunt said he was hopeful that there would be success in negotiations at the weekend, in time for the parliamentary vote.

Keir Starmer, Brexit spokesman for the opposition Labour party, said it was “increasingly clear Theresa May will not be able to deliver the changes she promised to her failed Brexit deal.”

“This speech looks set to be an admission of failure,” he said.