LONDON  - The Northern Irish party that props up Prime Minister Theresa May's government was in talks with British ministers on Friday to see what additional assurances would be needed for them to save her twice-defeated Brexit deal.

The United Kingdom's divorce from the EU has sown chaos throughout May's premiership and the Brexit finale is still uncertain. Options include a long delay, exiting with May's deal, leaving without a deal or even another referendum.

May has given Brexit supporters an ultimatum - ratify her deal by Wednesday or face a delay to Brexit way beyond June 30 that would open up the possibility that the entire divorce could be ultimately thwarted.

To succeed, May must win over dozens of Brexit-supporting rebels in her own Conservative Party and the Northern Irish Democratic Unionist Party (DUP), which has 10 lawmakers in parliament.

For the DUP, which could pull in some Brexit-supporting Conservative lawmakers behind a deal, the main issue is the Irish backstop - an insurance policy which sets out what happens to the Irish border if the sides fail to find another solution.

A DUP spokesman said the party was expected to give a progress report on the talks later on Friday.

In a last ditch attempt to save her deal, May is scrambling to win over the DUP and dozens of rebels in her own party.

Finance Minister Philip Hammond was in the meeting with the DUP, news that at one point pushed the pound to its highest level of the day against the dollar. [GBP=D3}

May says she wants to minimise any delay in leaving the EU to just three months, but to achieve that she will need parliament to back her deal at the third time of asking early next week, possibly Tuesday.

Many Brexiteers and the DUP fear the backstop, aimed at avoiding controls on the border between the British province of Northern Ireland and EU-member Ireland, will trap the United Kingdom in the EU's orbit indefinitely.

May's deal, an attempt to keep close relations with the EU while leaving the bloc's formal structures, was defeated by 230 votes in parliament on Jan. 15 and by 149 votes on March 12.

(Writing by Guy Faulconbridge; editing by Michael Holden and Janet Lawrence and Jon Boyle) ((guy.faulconbridge@thomsonreuters.com; 07825218698;))