LONDON (AP) -- The British Parliament was set to vote on competing Brexit plans Tuesday, with Prime Minister Theresa May desperately seeking a mandate from lawmakers to help secure concessions from the European Union.
Legislators were delivering verdicts on proposals that have been submitted by both pro-Brexit and pro-EU legislators since Parliament rejected May's divorce deal with the bloc two weeks ago, leaving Britain lurching toward a cliff-edge "no-deal" departure on March 29.
May insists her agreement can still win Parliament's backing, if it is tweaked to alleviate concerns about a contentious Irish border provision. EU leaders are adamant that the measure can't be renegotiated, whatever British lawmakers decide.
The border measure, known as the backstop, would keep the U.K. in a customs union with the EU in order to remove the need for checks along the frontier between the U.K.'s Northern Ireland and EU member Ireland after Britain leaves the bloc.
Opposition to the backstop by pro-Brexit lawmakers — who fear it will trap Britain in regulatory lockstep with the EU — helped sink May's deal on Jan. 15, when Parliament rejected it by 432 votes to 202.
May has backed a proposal calling for the backstop to be replaced by "alternative arrangements," and has called on all lawmakers from her Conservative Party to support it.
International Trade Secretary Liam Fox said the amendment offered the best chance for Britain to avoid leaving the EU without a deal on future relations.
"I think we should send the prime minister back to Brussels with a strong mandate to be able to say 'If you compromise with us on this one issue, on the backstop, we would be able to a get an agreement,'" he told the BBC.
But it's far from certain the amendment can win support from a majority in the House of Commons. And the EU insists the legally binding withdrawal agreement cannot be renegotiated.
Ireland's European Affairs Minister, Helen McEntee, said British politicians needed to show "a bit of realism."
"There can be no change to the backstop. It was negotiated over 18 months with the U.K. and by the U.K.," she said.
Though Parliament is overwhelmingly opposed to May's deal, lawmakers are divided over what to do instead — whether to brace for a "no-deal" Brexit or to try and rule it out.
Much of the business world says a no-deal Brexit would cause economic chaos by eliminating existing EU trade agreements and imposing tariffs, customs checks and other barriers between the U.K. and its main export market.
To complicate matters further, the split between Brexiteers and pro-Europeans runs through both main parties, Conservatives and Labour.
Conservatives from rival wings of the party proposed a compromise Tuesday that calls for Britain to seek a "new backstop" and an extended transition period of almost three years after March 29 so that Britain and the EU can work out a permanent new trade deal.
But Sarah Wollaston, a pro-EU Conservative, dismissed the plan as "fantasy Brexit."
She tweeted: "There won't be any renegotiation of the Withdrawal Agreement & all the nonsense is a smokescreen whilst the clock runs down to No Deal. Parliament should vote to reject that catastrophe."
The backstop proposal is one of more than a dozen amendments proposed by lawmakers that aim to alter the course of Britain's departure. Some others seek to rule out a no-deal Brexit so Britain can't tumble out of the bloc on March 29 without an agreement in place to cushion the shock.
Speaker of the House of Commons John Bercow will announce before Tuesday's debate begins which amendments have been selected for votes.