British Prime Minister Theresa May said on Sunday she would be "armed with a fresh mandate and new ideas" when she next meets European Union negotiators over her Brexit deal.
EU officials have insisted that the deal -- rejected by British lawmakers -- is not open for renegotiation.
But May wrote in the Sunday Telegraph that she would be "battling for Britain and Northern Ireland" in her efforts to get rid of the agreement's unpopular "backstop" provision.
"If we stand together and speak with one voice, I believe we can find the right way forward," she said.
The so-called backstop is intended to ensure there is no return to a hard border with Ireland, but Brexit supporters fear it will keep Britain tied to the EU's customs rules.
MPs voted last week to send May back to Brussels to renegotiate the clause, suggesting her deal would then be able to pass after it was roundly rejected in parliament last month.
"I am now confident there is a route that can secure a majority in the House of Commons for leaving the EU with a deal," she wrote.
"When I return to Brussels I will be battling for Britain and Northern Ireland, I will be armed with a fresh mandate, new ideas and a renewed determination to agree a pragmatic solution."
The EU insists that the deal "remains the best and only way to ensure an orderly withdrawal", and German Foreign Minister Heiko Maas said Sunday that "if the British want to avoid a disorderly Brexit, our offer is on the table".
But with the clock running down until the March 29 exit date the risks of a no-deal Brexit for both Britain and the bloc are coming into sharp focus.
Car giant Nissan announced Sunday it was cancelling plans to build its X-Trail SUV at its plant in northeast England, saying that "the UK's future relationship with the EU is not helping".
May said opposition leader Jeremy Corbyn "also believes the potential indefinite nature of the backstop is an issue", and that the EU has "already accepted the principle of 'alternative arrangements' superseding the backstop should it ever be required".
The backstop would kick in if Britain and the EU have not agreed a trade deal on their future relationship after a time-limited transition period of up to two years.
- Nissan blow -
The prime minister rejected accusations that plans to reopen the backstop talks risked upsetting the Irish peace process.
"Nor do I have time for those who believe the verdict passed by the British people in 2016 should be overturned before it is even implemented," she added, referring to the rump of MPs calling for a second referendum.
"I'm determined to deliver Brexit, and determined to deliver on time -- on March 29, 2019," she wrote.
May has promised MPs that she will bring any revised deal back to be voted on by MPs on February 13.
Warnings of the consequences of a no-deal Brexit intensified last week as several multinational firms, including Airbus and Ford said jobs could suffer with an unfavourable negotiating outcome.
Nissan dealt another blow on Sunday by announcing it was shifting future investment away from its largest European plant in Sunderland, northeast England, which employs 7,000 people.
The car giant announced in 2016 that it planned to build its X-Trail model in Sunderland, but will now assemble it instead at Nissan's global production hub in Kyushu, Japan.
Queen Elizabeth II was even drawn into the fray, with the Sunday Times reporting that the civil service had drawn up plans to whisk away the royal family to a secret location if riots should break out due to no deal, with Buckingham Palace declining to comment on the report.
The Brexit saga has driven a wedge in the heart of both major parties, pitting centrists against their more ideologically driven MPs.
Several rebellious centrist Labour MPs, who want a soft Brexit or to stay in the EU, are mulling forming a new party, according to Sunday's Observer.
They are disillusioned with the ambiguous stance taken by leftist leader Jeremy Corbyn, who has been a long-term eurosceptic but said he voted to Remain in 2016.