Theresa May has held telephone talks with DUP leader Arlene Foster after Brexit negotiations with the EU stalled over the Irish border.
The prime minister pulled out of a potential deal on Monday after meeting fierce resistance from Democratic Party Unionists about the proposals.
It comes after the party said it will not accept any Brexit deal that “separates” Northern Ireland from the rest of the UK with a hard border.
ITV News Political Editor Robert Peston said the phone call was a “gesture” and no progress had been made over the border issue.
He added that the government’s hopes to conclude a deal by Sunday appeared to be “ambitious”.
Mrs May had expected to speak to Mrs Foster on Tuesday but the call did not take place.
The DUP leader has complained that her party got a “big shock” and was only shown the proposed text of Mrs May’s offer to the EU regarding the Irish border, hours before the parties hoped to announce an agreement.
“That is something that came obviously, as a big shock when we’d looked at the wording and seen the import of all that.”
“We that knew we couldn’t sign up to anything that was in the text that would allow a border to develop in the Irish sea,” she added.
The EU insists trade negotiations can begin only after “sufficient progress” has been made on the three key divorce issues of the Irish border, citizens’ rights, and the UK’s exit bill.
Mrs May and European Commission President Jean-Claude Juncker hope to reconvene later this week for more talks ahead of the summit of the European Council on December 14.
Foreign Secretary Boris Johnson has called on the EU to give an immediate green light to talks on post-Brexit trade relations, rather than insisting on waiting for a breakthrough over the Irish border.
“We will come up with a solution, but the important thing is that that solution can only be discovered in the context of discussions on the end-state of the UK’s relations with the rest of the EU.
He added: “What I would say is that the best way to sort it out is to get on to the second phase of the negotiations, where all these difficult issues can be properly teased out, thrashed out and solved.”