Boris Johnson, the favourite to become British prime minister, said he will seek a new Brexit deal with the European Union but if the bloc refuses his demands then he will lead the world's fifth largest economy out without agreement on October 31.
The United Kingdom's three-year Brexit crisis could be about to deepen as Johnson's pledge to leave the EU with or without a deal on Halloween could provoke a standoff with the British parliament which has indicated its opposition to a no-deal exit.
No-deal means there would be no transition period so the exit would be abrupt, the nightmare scenario for many business leaders and the dream of hard Brexiteers who want a decisive split.
Seeking to turn the public discourse away from a discussion about an argument with his girlfriend, Johnson told the BBC he would pick the bits of Theresa May's "dead" Withdrawal Agreement that he likes and seek a new deal with the EU.
"My pledge is to come out of the EU at Halloween on 31 October," said Johnson, 55, adding that there were "abundant technical fixes" to prevent the return of a hard border between Ireland and the United Kingdom's Northern Ireland.
He repeated a warning that there would be "creative ambiguity" about when and how a previously agreed 39 billion pound ($50 billion) exit bill gets paid.
The EU has refused to renegotiate the Withdrawal Agreement reached with May last November, and Ireland has indicated it is not willing to change the Irish border "backstop" that upset the Northern Irish party which props up May's minority government.
Johnson said he did not want a no-deal Brexit - which investors warn would roil financial markets and send shockwaves through the European economy - but that it was necessary to put it on the table so that Britain could get the result it wanted.
"The way to get our friends and partners to understand how serious we are is finally, I'm afraid, to abandon the defeatism and negativity that has enfolded us in a great cloud for so long and to prepare confidently and seriously for a WTO or no-deal outcome," he told BBC TV.
Britain is a member of the World Trade Organisation so tariffs and other terms governing its trade with the EU would be set under WTO rules.
Business leaders have already triggered contingency plans to cope with additional checks on the post-Brexit UK-EU border they fear will clog ports, silt up the arteries of trade and dislocate supply chains in Europe and beyond.
Brexit supporters say there would be short-term disruption but in the long-term the UK would thrive if cut free from what they cast as a doomed experiment in German-dominated unity that is falling behind China and the United States.
Australian Associated Press