Many in Brussels thought Sanchez was trying to score points with voters at home before a Dec 2 local election in the southern Andalusia region. They said the issue could be solved by the leaders and warned Madrid not to put the whole Brexit agreement at risk.

As an olive branch to Brexit campaigners in Britain, May was seeking to include their proposed technological solutions to keep the border open on the island of Ireland. The EU has previously dismissed these ideas as unrealistic at this stage.

May's finance minister, Philip Hammond, said Britain's parliament needed to back her deal or risk either seriously damaging the economy or jeopardising Brexit altogether.

"A smooth exit from the European Union - doing this in an orderly fashion - is worth tens of billions of pounds to our economy," he told broadcaster ITV.

"If the deal is not approved by parliament, we will have a politically chaotic situation ... In that chaos that would ensue, there may be no Brexit," he added.

NORTHERN IRELAND

The British and European parliaments must ratify the tentative deal to end more than 40 years of partnership before Brexit day on March 29, 2019, or Britain would be set to crash out of the EU with no treaty.

The publication last week of a draft exit treaty sparked the biggest crisis of May's premiership, with two cabinet ministers quitting and dozens of Conservative members of parliament calling on her to step down. They accuse May of making too many concessions to the EU, while others oppose Brexit altogether.

May hopes the blueprint on future relations - a political document of about 20 pages meant to be agreed side-by-side with the legally binding 600-page exit treaty -- will help win back enough support at home for her approach to pass in parliament.

The Northern Ireland party that props up May's government said it does not plan to withdraw its support yet despite opposition to her withdrawal deal.

"The confidence and supply agreement ... is very much still in existence," Democratic Unionist Party leader Arlene Foster told the BBC broadcaster.

Asked when the party might consider pulling the plug on support for May, Foster said: "We're not there yet."

Despite the political turmoil around her, May has shown no sign in public of any doubt that she can bring home a deal.

The draft treaty envisages Britain staying in a customs union with the bloc, which many Brexit supporters see as a compromise too far.

The EU is trying to discourage Britain from any renegotiation of the draft treaty, while also seeking to assuage concerns expressed by some of the remaining 27 member states. While unanimity among the 27 is not legally required to endorse the deal now, the bloc seeks a unified stance.

DEMANDS

Both sides have also been advancing contingency plans for the worst case scenario - a no-deal Brexit.

Diplomats in Brussels said Britain was also seeking an easy flow of goods after Brexit, a position which was too close to the privileges allowed only for countries that sign up to EU single market rules, including free flow of people and services.

"The UK wants free movement of goods, which they won't get because that's back to discussing partial access to the single market, which we don't do," another diplomat said.

In addition, France has called for more guarantees on future access to Britain's fishing waters, which London wants to keep firmly under its control after Brexit.

Most in the EU are determined to get the deal over the line, with a third EU diplomat saying: "There is plenty of negotiating time left to achieve that."

Reuters