The message from British prime minister Theresa May and European commissioner Jean-Claude Juncker was clear: This is not a failure.

It certainly looks, sounds, and feels like a failure, however. May set out to Brussels yesterday expecting to return home with a deal on the three issues — the Northern Ireland border, citizens’ rights and the amount of money the UK will pay as it leaves the EU — standing in the way of trade. She didn’t manage to do it.

Both sides said though they were hopeful of getting a deal by the end of the week.

After a steady rise yesterday the pound dropped sharply this morning on uncertainty over Brexit as May scrambled to revive the deal — on track for its worst fall in a month.

May and her team — including chief whip Julian Smith — will embark on an intense round of diplomacy to try to persuade the DUP, whose 10 MPs prop up the the prime minister’s minority government, to drop their veto.

It’s thought Arlene Foster, the DUP leader, may have rejected the proposed deal covering the north-south border in Ireland after incomplete details of the agreement were leaked from Dublin.

May is due to update ministers at a cabinet meeting this morning.

Peter Ricketts, former permanent secretary at the Foreign Office, told BBC Radio 4’s Today programme:

We are used to prime ministers going to Brussels to have a row with the EU … but to go to Brussels, to go, agree with the EU and then have a row with your own side is inconvenient. That will knock confidence in doing the final deal. We may be shown in the next few days that it all comes right but as of now, yes it’s done damage.

Theresa May is likely to be back in Brusseles tomorrow – though it’s unclear whether she would meet Juncker and chief Brexit negotiator Michel Barnier.