BRUSSELS - UK government ministers talked up the chances of salvaging a Brexit deal as Prime Minister Theresa May prepared for more meetings in Brussels on Wednesday that few in the European Union believe can overcome the deadlock in negotiations.

Britain is due to leave the EU on March 29, but diplomats say London effectively now has less than a month to find a solution as it would have to be agreed about a week before a regular summit of the bloc's national leaders on March 21-22.

The EU refuses to bin a protocol on the Irish border which prompted UK lawmakers to reject May's deal last month. Complicating May's task in finding a solution, three members of her ruling Conservative Party quit on Wednesday over the government's "disastrous handling of Brexit".

Foreign minister Jeremy Hunt said on Wednesday he remained "hopeful" of a resolution. He stressed the role of Attorney General Geoffrey Cox in being persuaded by concessions from the EU to change his legal advice that the so-called Irish "backstop" could bind Britain forever to EU rules.

Many on the continent stress that the backstop - an insurance policy for avoiding customs checks on the new EU-UK border with Britain's troubled province of Northern Ireland - was proposed by May herself and gives Britain benefits in trade that EU states do not want to last longer than needed.

On both sides, officials highlight a determination to put in place, as stated in November's Withdrawal Agreement, "alternative arrangements" to allow goods to cross the Irish border unchecked while also, through the use of new technology, to respect differing UK and EU customs and other rules.

However, Brussels has been resisting a push by May, forced by rebels in her own Conservative party, to reopen that treaty to replace the backstop with agreed alternatives now or put a time limit on the backstop or give Britain a veto on its use.

Brexit Secretary Stephen Barclay, who has been shuttling to Brussels with Cox and is due back later in the week, said on Tuesday that alternatives involving technology would avoid the need for the backstop after a status-quo transition period ends.

But he did not mention those being part of a revised exit treaty. British finance minister Philip Hammond said on Tuesday it was clear the EU would not now consider alternatives to the Irish backstop but that such options could be valuable in the future.

BREXIT "FOR SLOW LEARNERS"

The pound surged against the dollar on Tuesday on raised hopes that a compromise - whereby the EU would offer further assurances that the backstop would either never be used or be used only for a very short time - could unlock a deal and avoid serious disruption to the economy after March 29.

It slipped back again on Wednesday as worries about May's ability to get any compromise through parliament, which is split among those unlikely to accept any deal that works for the EU, those who want Brexit stopped and those who support May's plan.

Complicating May's task, three pro-EU members of her party said they were joining a new independent group in parliament set up by seven former lawmakers of the opposition Labour Party, whch is as divided over Brexit as the Conservatives.

Speaking in Berlin, Hunt said: "I think what has changed in the last four weeks is that we can now see a way to get a parliamentary majority for the Withdrawal Agreement."

EU diplomats said time was fast running out.

"They have until March 10, maybe March 15 at the latest," one EU diplomat said. "Otherwise they will be forced into a delay of Brexit, or crash out."

Many officials believe that, come what may, Britain will have to ask for a delay to the March 29 deadline, just to give it time to pass further legislation ahead of its departure.

EU diplomats say Barclay and Cox - now central in renewed Brexit talks since the House of Commons voted down May's deal in January - may slowly be coming around to understanding the bloc's position.

"It's Brexit for slow learners," said one EU diplomat saying the British side had so far failed to propose any new solutions on the backstop issue beyond those already rejected by the bloc.

But the EU hopes that, under growing pressure of looming no-deal disruptions, Britain would eventually accept assurances the bloc has already offered in January and December, repackaged in a legally-binding way.

May is keen to get some EU concessions before Feb.27 when the House of Commons is due to vote again on Brexit options. But the bloc is wary of offering anything now to see it sink again in the divided UK parliament.

"It's too early for a breakthrough," another EU diplomat said. "The second half of March is the make-or-break moment."

(Additional reporting and writing by Alastair Macdonald and Elizabeth Piper in London; Editing by Gareth Jones) ((alastair.macdonald@thomsonreuters.com; Reuters Messaging: alastair.macdonald.thomsonreuters.com@reuters.net))