LONDON (BLOOMBERG) - Theresa May and the European Union are heading for a high-stakes, last-minute gamble that will decide whether the United Kingdom leaves the bloc with or without a deal, people familiar with both sides said.

On March 21 - just a week before Britain is due to exit the EU - the prime minister will have the chance to win a late concession from European leaders at a summit in Brussels, the people said.

The bloc is unlikely to offer sweeteners much sooner in case the British side asks for even more, according to one of the individuals, who asked not to be named.

As the deadline looms, Mrs May would then put her revised deal to Parliament in London to approve, forcing politicians to choose between an orderly divorce and a potentially chaotic no-deal Brexit that could hit the pound by as much as 25 per cent.

While some ministers in Mrs May's government believe the threat of an economic disaster will force her opponents to back her plan, other government officials believe such a strategy is too risky and must be stopped.

RUN THE CLOCK DOWN

Mr Keith Simpson, a usually loyal Conservative, said Mrs May is using dangerous delaying tactics, warning that he would not accept a no-deal Brexit.

"Her scheme is to run the clock down so people are more likely to accept her deal," Mr Simpson said. "It's a high-wire act and - gulp - might lead to a no-deal."

The UK is on course to plunge out of the EU with no new trade agreement in place on March 29. The divorce accord that Mrs May spent a year and a half negotiating was overwhelmingly rejected in a parliamentary vote on Jan 15.

In the month since that record defeat, Mrs May has been trying to get agreement for changes to the divorce package to make it acceptable to members of Parliament.

Mrs May spent 2½ hours on Tuesday (Feb 12) urging the House of Commons to give her more time to negotiate better terms. She faced accusations that she is deliberately looking to kill time off the clock in order to blackmail Parliament into backing her blueprint.

According to ITV News, Mrs May's chief Brexit negotiator, Mr Oliver Robbins, provided some evidence that her plan is to push Parliament to make a choice with just a few days left before exit day.

LATE MARCH STRATEGIES

Mr Robbins suggested the strategy would be to tell the Commons in the final week of March that if an amended version of the government's deal wasn't passed, talks would have to be extended, potentially for a long time, ITV reported on Tuesday.

Mrs May's office declined to comment on what it called "alleged remarks". Earlier in the day, the prime minister began clearing the path to rushing through a deal at a very late stage.

In Brussels, too, officials are drawing up options for concessions that would be offered to the UK at the last moment. These include an extra legal document that will probably make a binding commitment to try to end the Irish "backstop" as soon as possible.

While there is genuine anger in the EU at the way Mrs May has handled things since the deal was struck in November, both sides are complicit in the high-stakes strategy of running down time, one EU diplomat said.

The prime minister may not get the chance to do so until the final few days. Pro-EU members of Parliament will have an opportunity to take control of the divorce process away from Mrs May - to stop a no-deal split - on Thursday, and again potentially on Feb 27.