The European Union is being "a bit negative" concerning reaching a Brexit deal but it can be done, British Prime Minister Boris Johnson said on Tuesday evening.
"At the moment, it is absolutely true that our friends and partners are a bit negative ... but I think we'll get there. I think there is a real sense now that something needs to be done with this backstop," he told reporters.
"We think there's a big opportunity now for everybody to come together, take out that backstop and then ... in the course of the negotiations on the free trade deal ... which we're going to do after October 31, we will be bringing forward all the ways in which we can maintain frictionless trade at the Northern Irish border," he added.
European Council President Donald Tusk earlier rebuffed an attempt to reopen Brexit negotiations, saying a letter from Johnson included no "realistic alternatives" to the Irish backstop.
Johnson launched the attempt on Monday night, writing to Tusk seeking the removal of the Irish backstop from the existing deal.
In the letter, published by his office, Johnson repeated his calls for the device — an insurance policy to avoid the return of a hard border in Ireland — to be removed from the withdrawal agreement reached with his predecessor Theresa May.
In its place, he proposed a commitment to have alternative border arrangements by the end of a post-Brexit transition period.
"The backstop is insurance to avoid a hard border on the island of Ireland unless and until an alternative is found," Tusk said in a tweet.
"Those against the backstop and not proposing realistic alternatives in fact support re-establishing a border. Even if they do not admit it."
The European Union (EU) executive echoed Tusk's sentiments, saying the backstop was the only option identified by both the UK and the bloc to avoid a hard border on the island of Ireland post Brexit.
"The letter does not provide a legal operational solution," European Commission spokeswoman Natasha Bertaud told a news briefing.
"Our position on the backstop is well known... (It) is the only means identified so far by both parties to honour this commitment."
EU leaders have repeatedly indicated that they are unwilling to revisit the withdrawal agreement, which was the culmination of almost three years of discussions.
Finnish prime minister Antti Rinne on Monday "reiterated" to Johnson that the EU would not renegotiate the Brexit deal, a spokesman said.
The British prime minister also held an hour-long telephone call earlier on Monday with his Irish counterpart, Leo Varadkar, according to officials. However, they appeared to have agreed on little except to meet in Dublin next month for further talks.
Varadkar repeated his stance that the withdrawal agreement cannot be reopened, officials said.
In his letter, Johnson said Britain was ready to look "constructively and flexibly" at what commitments could help provide confidence about what would happen if such arrangements were not fully in place at the end of that period.”
The backstop would force Britain to obey some EU rules if no other way could be found to keep the land border open between British-ruled Northern Ireland and EU member Ireland. Dublin says this is crucial to maintaining peace.
Johnson wrote that the backstop was "simply unviable" because it is "anti-democratic and inconsistent with the sovereignty of the UK as a state" but that he was committed to ensuring there was no return to a hard border.
"The government will not put in place infrastructure, checks, or controls at the border between Northern Ireland and Ireland. We would be happy to accept a legally binding commitment to this effect and hope that the EU would do likewise," Johnson wrote.
The EU has so far said the withdrawal deal cannot be renegotiated. Johnson is due to carry out his first foreign trip as prime minister this week to meet with German Chancellor Angela Merkel and French President Emmanuel Macron.
"Time is short. But the UK is ready to move quickly, and, given the degree of common ground already, I hope that the EU will be ready to do likewise," he wrote to Tusk.