LONDON (Reuters) - Prime Minister Theresa May’s warned lawmakers that unless they approved her Brexit divorce deal after two crushing defeats, Britain’s exit from the European Union could face a long delay and could involve taking part in European parliament elections.

FILE PHOTO: British Prime Minister Theresa May walks outside Downing Street, as she faces a vote on Brexit, in London, Britain March 13, 2019. REUTERS/Henry Nicholls/File Photo

After two-and-a-half years of tortuous divorce negotiations with the EU, the final outcome is still uncertain with options including a long delay, exiting with May’s deal, a disorderly exit without a deal or even another referendum.

May has issued Brexit supporters a clear ultimatum - ratify her deal by a European Council summit March 21 or face a delay to Brexit way beyond June 30 that would open up the possibility that the entire divorce could be ultimately thwarted.

The prime minister bluntly warned that Britain will be forced to take part in European parliamentary elections expected to place at the end of May if there is a longer extension to Brexit talks.

“If the proposal were to go back to square one and negotiate a new deal, that would mean a much longer extension – almost certainly requiring the United Kingdom to participate in the European Parliament elections in May,” she said in an article in the Sunday Telegraph.

“The idea of the British people going to the polls to elect MEPs three years after voting to leave the EU hardly bears thinking about. There could be no more potent symbol of parliament’s collective political failure.”

EU leaders will consider pressing Britain to delay Brexit by at least a year to find a way out of the domestic maelstrom, though there is shock and growing impatience at the political chaos in London.

Her 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.

But May continues to fight to build support for her plan, which is expected to put before lawmakers for a third time next week, possibly on Tuesday.

To get it through parliament, the prime minister must win over dozens of Brexit-supporting rebels in her own Conservative Party and the Northern Irish Democratic Unionist Party (DUP) which props up her minority government.

The DUP said it is continuing to hold talks with the government over the weekend but differences remained over the Irish border.

The changes would address the DUP’s concerns over the backstop - an insurance policy aimed at avoiding controls on the sensitive border between the British province of Northern Ireland and EU member Ireland. The backstop is the most contentious part of the divorce deal the government has agreed with the EU.