Updated 4pm with the announcement that vote is still on - Britain's Brexit minister insisted a crucial vote on Prime Minister Theresa May's Brexit deal would go ahead after a newspaper report on Sunday that she planned to delay it and make a last-minute dash to Brussels to seek a better offer.
Several pro-Brexit former government ministers on Sunday piled pressure on May to go back to the European Union and renegotiate a deal that has won little support among lawmakers both in her own Conservatives and opposition parties.
May's deal looks set to be rejected by parliament on Tuesday, a decision that would throw plans for Britain's exit from the EU into turmoil and leave her own political future hanging in the balance.
The Sunday Times reported May was expected to announce on Monday that she was delaying the vote to head to Brussels to make a final appeal to the EU to improve Britain's exit deal.
"The vote is on Tuesday, that is what we are focused on," Brexit minister Stephen Barclay told BBC TV on Sunday.
"The risk for those who say simply go back and ask again, the risk is that isn't necessarily a one-way street, the French the Spanish and others will turn round, if we seek to reopen the negotiation, and ask for more," he added.
Barclay said Britain would enter "uncharted waters" if it loses the vote, but May could stay on as prime minister.
There has been speculation May might use an EU summit on Dec. 13-14 to press for changes to the deal.
The strongest opposition centres around the so-called backstop, an insurance policy designed to prevent a hard border between EU member Ireland and British-ruled Northern Ireland.
Brexit supporters and May's nominal allies in Northern Ireland's Democratic Unionist Party say it could leave Britain forced to accept EU regulations indefinitely, or Northern Ireland treated differently from the rest of the United Kingdom.
EU supporters say Britain would become little more than a rule-taker, offering the worst of all worlds.
Several lawmakers, including the DUP's leader in the British parliament, Nigel Dodds, former Brexit minister Dominic Raab and former work and pensions minister Esther McVey, on Sunday called for May to go back to Brussels and seek to renegotiate the deal.
Nothing is over until it is over- Boris Johnson
Former foreign secretary Boris Johnson, a leading Brexit campaigner, said lawmakers on all sides were united against the backstop and losing the vote in parliament would give May a mandate to ask the EU to remove it from the deal.
"Nothing is over until it is over," he told BBC TV.
"If the prime minister is able to go back to Brussels this week and say I'm afraid that the Irish backstop solution that you have come up with is very unpopular ... they will listen."
While EU diplomats have said they could consider helping May with "cosmetic" changes to the non-binding political agreement that accompanies the deal, the legally binding text of the exit deal itself would be off limits to renegotiation.
"GRAVE UNCERTAINTY"
In an interview in the Mail on Sunday, May told lawmakers the choice was her deal or the risk of "grave uncertainty" for Britain and the chance of no Brexit, or leaving the EU without a deal.
Ahead of the vote, the EU's top court will say on Monday whether Britain can unilaterally halt its exit from the EU, due to take place on March 29, 2019.
May said rejecting her deal would also risk the opposition Labour Party getting into power. Labour could seek to take control of the country by calling a vote of no confidence in the government if May's deal is voted down.
May also risks being ousted by her own lawmakers.
Leading pro-Brexit Conservative Jacob Rees-Mogg, who has previously called for a leadership contest, wrote in the Mail on Sunday that May should stand down, whether her deal is defeated in parliament's House of Commons or she seeks to delay the vote.
"The humiliation of avoiding a Commons vote is as much a reason for her departure as defeat in an actual vote," he said.
Former minister Esther McVey, who resigned over May's deal last month, also said it would be "very difficult" for the prime minister if she doesn't go back to the EU and get a better deal.
But Johnson, who is seen as a possible successor to May, said she could stay on and go back to the EU to renegotiate the deal if she loses the vote.
"What people want to hear now is not stuff about leadership elections and personalities, what they want to hear is that there a plan to get out of this mess," he said.