By Elizabeth Piper, Kylie MacLellan and William James
LONDON (Reuters) - Prime Minister Theresa May piled pressure on rebel lawmakers on Thursday to back her battered European Union divorce deal as parliament prepared to vote on seeking a delay to Britain's departure that could ultimately derail the process.
Just 15 days before Britain is due to leave the European Union, May is using the threat of a long delay to push Brexit supporters in her Conservative Party finally to back her deal.
That vote could come next week, when those lawmakers will have to decide whether to back a deal they feel does not offer a clean break from the EU, or accept that Brexit could be watered down or even thwarted by a lengthy delay.
In the meantime, the future direction of the world's fifth largest economy remains up in the air.
May's authority hit an all-time low this week after a series of humiliating parliamentary defeats and rebellions. But she has made clear her plan is still on the agenda, despite twice being rejected by an overwhelming majority in parliament, in January and again on Tuesday.
"The path ahead and the choices that confront us are far from straightforward: We need to decide how long an extension to propose and we need to put that proposal to the European Council before they meet next week," May's de facto deputy David Lidington told parliament ahead of Thursday's vote.
May's spokesman said she would put her Brexit deal, struck after two-and-a-half years of negotiations with the EU, to another vote "if it was felt that it were worthwhile".
Seeking to win over dissenters, she has given rebellious Conservative lawmakers a thinly-veiled warning that a failure to back her plan could mean no Brexit at all.
Britons voted by 52-48 percent in a 2016 referendum to leave the EU, a decision that has not only divided the main political parties but also exposed deep rifts in British society.
"SHE DIDN'T LISTEN"
U.S. President Donald Trump, who had earlier said he looked forward to negotiating a "large scale" trade deal with Britain after Brexit, added to May's headaches by criticizing her handling of the crisis.
"I will tell you, I'm surprised at how badly it's all gone from the standpoint of a negotiation," Trump told reporters in the Oval Office as he met Irish Prime Minister Leo Varadkar.
"But I gave the prime minister my ideas on how to negotiate it and I think you would have been successful. She didn't listen to that, and that's fine. But I think it could have been negotiated in a different manner, frankly."
Although parliament on Wednesday voted against the prospect of a no-deal Brexit, the vote had no legal force and the default position if nothing else is agreed remains that Britain will exit on March 29 without a transition arrangement.
Business leaders warn that this would cause chaos. Brexit supporters say that, in the longer term, it would allow Britain to forge trade deals across the world and thrive.
EU leaders meeting next Thursday - who would need to approve any extension - will consider pressing Britain to delay Brexit by at least a year, European Council President Donald Tusk said.
"I will appeal to the EU27 (remaining members) to be open to a long extension if the UK finds it necessary to rethink its Brexit strategy and build consensus around it," he said.
France said that a short Brexit delay merely to discuss May's existing deal was "out of the question".
But there was no sign that the prospect of a long delay - which could lead to Britain keeping closer ties to the EU than May had planned, or even a second Brexit referendum - was causing a major shift in the views of Conservative hardline euroskeptics who have so far thwarted her.
"SCORCHED EARTH"
Lawmaker Andrew Bridgen accused her of pursuing a "scorched earth" policy of destroying all other Brexit options to leave lawmakers with a choice between her deal and a long delay.
May also needs to win over the Northern Irish Democratic Unionist Party (DUP) that props up her minority government in parliament, which has so far refused to back her plan.
DUP leader Arlene Foster said the party was working with the government to try to find a way of leaving the EU with a deal.
Sterling hit nine-month highs against the U.S. dollar and a nearly two-year high against the euro on Wednesday as investors saw less chance of Britain leaving the EU without a transition deal. It lost some of those gains on Thursday.
Lawmakers will vote on up to four amendments to May's Brexit delay motion from 1700 GMT (1 p.m. ET) on Thursday.
One calls for a second referendum on leaving the EU.
Another, proposed by the opposition Labour Party, calls for May to use a Brexit delay to give parliament time "to find a majority for a different approach".
A third would allow lawmakers to force a discussion of alternative Brexit plans. The fourth opposes the government bringing May's deal back unchanged for a third time.