German Chancellor Angela Merkel (left) shakes hands with British Prime Minister Theresa May as she arrives at the Chancellery in Berlin on Tuesday. John Macdougall/AFP

British Prime Minister Theresa May on Tuesday met Angela Merkel, Europe's most powerful leader, to seek support for a new Brexit delay while her ministers tried to break the deadlock in London at crisis talks with the opposition Labour Party.

More than a week after the United Kingdom was originally supposed to have left the EU, the weakest British leader in a generation has said Brexit might never happen as she battles to get a divorce deal ratified by a divided parliament.

With little sign of a resolution in London, May dashed to Berlin ahead of a meeting with French President Emmanuel Macron, to seek support for her request to delay Brexit a second time, from April 12 to June 30.

May met Merkel at her riverside Chancellery, a short walk from the Brandenburg Gate, where Ronald Reagan in 1987 urged Mikhail Gorbachev to "Tear down this wall!" - the barrier that had divided West and East Berlin since 1961.

While Merkel and May discussed Brexit inside, the opposition liberal FDP party drove an advertising van past the chancellor’s office with a message for May: "Dear Theresa May. Just do it. Stop Brexit. Make the most of Europe’s opportunities."

May and Merkel exchanged kisses on departure, with the German leader waving farewell as May headed to Paris to meet Macron at the Elysee Palace.

On the eve of an emergency EU summit in Brussels, chief EU Brexit negotiator Michel Barnier said the bloc was ready to grant a delay, but that the duration "has got to be in line with the purpose of any such extension".

"Any extension should serve a purpose. The length should be proportional to the objective. Our objective is an orderly withdrawal," Barnier told a news conference in Luxembourg.

"No-deal will never be the EU's decision. In order to avoid no-deal, the UK needs to agree to a deal," Barnier said.

Reuters