“The Prime Minister set out that the United Kingdom will be leaving the EU on Oct. 31 whatever the circumstances, and that we absolutely want to do so with a deal,” a spokeswoman said, adding that "the PM was also clear however that unless the Withdrawal Agreement is reopened and the backstop abolished there is no prospect of that deal.”
Britain is on course for a no-deal exit on Oct. 31 unless parliament can stop it or a new deal is reached with the EU.
The British parliament has rejected three times the withdrawal deal agreed between the last government and the EU, deepening a three-year crisis that threatens Britain's status as one of the world's pre-eminent financial centers and a stable destination for foreign investors.
Johnson wants the backstop removed from the deal.
He discussed his demands with Juncker in a "positive and substantive" 20-minute phone call on Tuesday following talks last week with German Chancellor Angela Merkel, French President Emmanuel Macron and European Council President Donald Tusk.
Juncker said he was willing to look at any concrete proposals on alternatives to the backstop, as long as they were compatible with the Withdrawal Agreement, according to a readout of the call from the European Commission.
Britain said it was working "at a pace to find a wide range of flexible and creative solutions" for the border with Ireland after Brexit, but it said the border discussion should be separate to the withdrawal deal.
"We are ready to negotiate in good faith an alternative to the backstop with provisions to ensure the Irish border issues are dealt with where they should always have been: in the negotiations on the future agreement between the UK and EU," a government spokeswoman said.
Johnson's Brexit adviser David Frost is due in Brussels on Wednesday to discuss the backstop with the Commission.
EU officials say they are listening to Johnson's arguments to replace one of the most hotly contested elements of the divorce agreement, something the bloc has previously said it will not agree to. A British official said it was felt there had been a softening in the EU's rhetoric around the backstop.
"It's good that there is a vibrant discussion, ideas are put forward but it's up to the U.K. government to come up with concrete proposals that would be compatible with the Withdrawal Agreement," European Commission spokeswoman Mina Andreeva stated.
Juncker underlined to Johnson that the EU's support for Ireland was steadfast and it was very attentive to the country's interests.
While Irish Foreign Minister Simon Coveney said Britain's proposals did not yet come close to what was needed.
"I think we need to be honest here, that the alternative arrangements that have been discussed to date do not do the same job as the backstop, not even close," Coveney said in Prague following a meeting with Czech Foreign Minister Tomas Petricek.
"So let's not pretend that solutions exist when they might not."