British Prime Minister Boris Johnson will speak to German Chancellor Angela Merkel, French President Emmanuel Macron and European Commission President Jean-Claude Juncker by the end of Monday in an attempt to urge the leaders to support his Brexit deal, the Sunday Times reported.

Negotiators for Britain and the EU have entered intense talks over the weekend to see if they can break the Brexit impasse before a crucial summit next week and a deadline for Britain to leave the bloc on October 31.

Johnson will offer the three leaders the option to either help him deliver a new deal this week, or to agree on a friendly version of no-deal Brexit by October 31, the newspaper said, citing a source familiar with the conversations.

The next few days will be critical if the British government is going to agree to departure terms with the EU, said a Downing Street source on Saturday, adding Britain remains a long way from agreeing to a final Brexit deal.

News of progress in the talks sent financial markets surging on Friday after Johnson and his Irish counterpart Leo Varadkar identified a pathway to a deal following months of acrimony.

But on Saturday, the deputy leader of the Northern Irish party which holds a key role in the talks signaled his concern about the mooted proposal and the Downing Street source said Britain remained ready to leave without a deal if needed. "We've always wanted a deal," the source said, on condition of anonymity. "It is good to see progress, but we will wait to see if this is a genuine breakthrough."

"We are a long way from a final deal and the weekend and next week remain critical to leaving with a deal on October 31. We remain prepared to leave without a deal on October 31."

The Sunday Times newspaper reported that Johnson, the face of Britain's 2016 campaign to leave the EU, was now "desperate" to secure a deal after security chiefs warned that leaving in a disorderly manner could inflame tensions in Northern Ireland.

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Meanwhile, pro-remain MPs claimed that they had gained sufficient votes to push for a second Brexit referendum as fresh doubts and fear were raised over Johnson's Brexit plan, ahead of the "super Saturday" showdown in parliament next weekend.

Ireland has proved the toughest nut to crack in the Brexit talks, specifically how to prevent the British province of Northern Ireland becoming a backdoor into the EU's markets without having border controls.

Ireland fears controls on the 500-kilometer (300-mile) border with Northern Ireland would undermine the 1998 Good Friday Agreement which ended three decades of sectarian and political conflict that killed more than 3,600 people.

Nigel Dodds, leader of DUP, questioned Johnson's proposed deal on Saturday, stressing that Northern Ireland "must stay in a full UK customs union, full stop." The 10 votes from DUP are crucial for Johnson to pass his plan in the parliament.

Labour, on the other hand said it is ready to whip its MPs to back a second referendum. "We believe we are getting closer to the majority it needs," said a source involved in the effort.

"The task now is maximizing that majority and seeing whether Johnson finally concedes that it is a way out for him too."

If Johnson has not secured a deal by October 19, he is obliged under the Benn act to ask the EU for an extension to UK membership until January 31.

(With input from Reuters)

(Cover: Anti-Brexit demonstrators are pictured protesting outside the Houses of Parliament in London, September 11, 2019. /VCG Photo)