The EU could show “generosity” and agree an extension of the Article 50 deadline to get Brexit talks back on track, London Mayor Sadiq Khan has said. 

As deadlock over the Northern Ireland border heightened fears the UK could crash out of the bloc on Friday, Khan was in Brussels to meet EU chief negotiator Michel Barnier. 

He believes the EU is “willing to listen” to concerns about the negotiations and could offer the UK more time.

It comes as the government insists the UK will be forced to choose between the deal Theresa May strikes or no deal, as the end of the two-year time limit to leave the bloc in March looms. 

The prime minister has insisted that a Brexit deal is 95% done, but talks have stalled, with May signalling she will trigger no-deal planning in the next three weeks. 

Khan is not part of the British negotiating team, but, as mayor of a city which voted 59.9% to remain in 2016, he was in Belgium to investigate whether Article 50 deadline could be extended in order for the UK to “reset” negotiations. 

Speaking after the meeting, he said: “It was really important to engage with him, to express to him the different views there are in our country.

“Theresa May doesn’t speak for the entire country when she talks about a bad Brexit deal or no deal whatsoever.

“I genuinely believe there is time for a better deal to be done. I genuinely believe there is a generosity, a goodwill on the part of the EU.

“My job is to also lobby my government to make sure they understand the consequences of a bad Brexit deal or or, even worse, no deal whatsoever.”

The mayor added: “I made the point that a bad Brexit deal, or even worse no deal whatsoever, it’s bad for London, it’s bad for our country but it is bad for the EU as well.

“He gets that. The point I’m sure he would make if he was here is that the ball is in the court of the British prime minister and it’s important that we understand the consequences of the Article 50 notice being served when it was.”

The Labour figure believes that an extension is in the interests of both sides to avert a “political and economic crisis”.

On Saturday, Khan was among the politicians who attended a march by around 700,000 of people through the capital, thought to have been the biggest anti-Brexit demonstration since the referendum in 2016.

But his overt backing for the second vote on whether to quit the EU has put him at odds with the Labour leadership.

Various frontbenchers have insisted a second referendum should only happen if the government fails to get a Brexit deal through Parliament and refuses to call a general election, and none of the shadow cabinet attended Saturday’s demonstration.

Khan’s meeting with Barnier comes a day after several senior figures from the smaller political parties met the negotiator in Brussels.

Lib Dem leader Sir Vince Cable, the SNP’s Westminster leader Ian Blackford, Plaid Cymru Westminster leader Liz Saville Roberts and Green MEP Molly Scott Cato held talks with the EU negotiator for an hour at his Brussels office on Thursday.

Last week, Tory pro-Brexiteers Iain Duncan Smith, Owen Paterson and Lord Trimble spoke with him in the Belgian capital.