Boris Johnson admitted that he needed EU cooperation to circumvent a hard Irish border or paralyze tariffs on trade in the event of disagreement.
In an exclusive interview with the BBC, the favorite of being the next prime minister said, "It's not just us."
But he said he "did not believe in it for a moment" Britain would go without an agreement, even though he was ready.
Asked about a dispute with his partner, he said it was "just unfair"
Reports on his girlfriend Carrie Symonds on Friday dominated the headlines on the weekend after the police were summoned to her London address.
In an interview with the Mr. BBC's political editor, Laura Kuenssberg, said Mr. Johnson that the existing agreement negotiated by Theresa May was "dead."
He insisted that it was possible to sign a new agreement with the EU before the end of October as the political landscape in Britain and on the continent has changed.
"I actually think that politics has changed so much since March 29," he said he referring to the original time limit for Brexit.
"I think there is a very different understanding of what is needed on both sides of the channel."
At present, Britain will leave the EU on October 31
Mr Johnson said he could convince Brussels to solve the Irish border issue – a key point – despite repeated warnings by EU leaders that this was impossible.
He said that "plenty of technical corrections" could be made to avoid border controls.
When complained that these do not exist yet, Mr. Johnson replied, "Well, they actually have, you have to a great extent, you've trusted dealer schemas, all sorts of schemes you could implement."
But he admitted there was "no magic bullet" to solve the problem.
A plan is full of ifs and buts
Mr. Johnson's controversial game is that he could sign a new trade agreement with EU leaders before the end of October.
And he says he could do that before the most controversial puzzle is solved – how to fix the dilemma across the Irish border.
He clearly believes he has the political skills to make that happen. He and his supporters would say that this is a plan.
But it's a plan full of ifs and buts – either heroic or daring assumptions, to imagine that the EU leaders and parliament would be willing to put their vision – and this until Halloween – to a very tight deadline to support.  The political pressure is not only directed to a speedy resolution, but also in a way that does not interfere with our relations with the rest of the world and the livelihood of the people living in this country.
Regarding the controversy surrounding his private life, even now, when he's on the threshold of # 10, it's absolutely clear that Boris Johnson thinks there are questions he simply does not have to answer.
And for a politician whose character many people doubt, who will follow him until he is ready to give more.
Mr. Johnson said that if he were elected, he would start new talks as soon as he reached Downing Street to discuss a free trade agreement.
He also said he hopes that the EU is ready to grant a period in which the status quo for a deal to be concluded after Brexit will be maintained.
He called this a "deadline for transposition", but accepted that this did not match the transposition deadline in the current draft treaty agreed with the EU.
Mr. Johnson pledged to pass new laws as soon as possible to ensure the rights of EU citizens living in Britain.
The former foreign minister also suggested that EU leaders could change their attitude to renegotiation because they have members of the Brexit party they do not want in their parliament and want to receive GBP 39 billion that were promised under the so-called divorce law.
He also said MEPs may be more willing to support a revised deal as they recognize that both main parties are "exposed to the real risk of extinction" if Brexit is blocked for a "good reason" to the events in his apartment in the early morning of Friday.
After quarreling with his partner Carrie Symonds, he had questions about his private life for three days.
"I do not talk about things that affect my family, dear ones," he said.
"And there is a very good reason for that, that is, if you do that, you draw them into things that really are." is not fair to them. "
Instead of his private life, he said the public really wanted to know" what's wrong with this guy "?
" Does he have confidence when it comes to character, then he delivers everything, what he promises?
Despite the widespread criticism of his conservative colleagues that he can not trust, Mr. Johnson said that anyone who questions his character speaks "absolute nonsense."
He also declined to comment on the allegations Leading rival Jeremy Hunt says he's a "coward" who avoids more direct televised debates and promises that he would "rule from the right center" in his election because "one wins" in the middle.
Mr. Johnson has agreed to attend an ITV event in two weeks, but Sky News has announced it will cancel a similar event planned for Tuesday as it would not attend.