SOUNDBITE (ENGLISH) BRITISH PRIME MINISTER, THERESA MAY, SAYING: "And I can say to the house with absolute certainty that there is no better deal available." The British Prime minister trying to sell her Brexit deal to parliament.

Theresa May has two weeks to rally lawmakers to support her future vision of the UK's relationship with the EU.

But they can either back it or reject it in a parliament vote set for mid-December.

A yes vote looks unlikely - and lawmakers pressed May on whether she had plan B.

SOUNDBITE (ENGLISH) BRITISH PRIME MINISTER, THERESA MAY, SAYING: "Because no one knows what would happen if this deal doesn't pass, it would open the door to more division and more uncertainty".

May might need to work on a fallback option and quickly.

She needs 320 lawmakers - not necessarily all from her own party - to agree with her in any vote.

But as Reuters political correspondent William James says, the maths doesn't look good.

(SOUNDBITE) (ENGLISH) REUTERS POLITICAL CORRESPONDENT, WILLIAM JAMES, SAYING: "So we've got a bloc of around 80-90 perhaps euro skeptics.

You'll probably be able to whittle that number down somewhat but it's certainly going to be a big number.

On the other side it's it's much smaller it's maybe 15 20 people who who have said they're going to vote against it because they want to stay in the European Union.

The reality is both sides are going to come down.

But the prime minister has no outright majority in parliament.

The Northern Irish party the DUP usually prop up her government in votes.

They've said they're not going to back this deal either." May's warned if the plan is voted down by parliament, the UK could then simply crash out of the EU with NO deal.

Especially as fellow European leaders have already made clear they won't reopen negotiations after signing off on her deal at the weekend.

(SOUNDBITE) (ENGLISH) REUTERS POLITICAL CORRESPONDENT, WILLIAM JAMES, SAYING: "The government has 21 days to come up with an alternative plan.

The reality is politics will overtake that.

We might see something very quickly afterwards.

The options are that May resigns.

We've seen that that's not in her nature she's she's very steadfast in kind of trying to see these things through.

They could try and come back for another vote." May's strategy is to push the pros of her deal.

Emphasizing it takes back control of money, laws, and borders.

Brexit campaigners though say it leaves Britain as little more than a vassal state, unable to break free from Brussels, but still subject to its regulations.