Brexit supporters wave Union flags as the time reaches 11 o'clock, in Parliament Square, venue for the Leave Means Leave Brexit Celebration in central London on Friday, the day the UK formally left the European Union. Photo: AFP

UK Prime Minister Boris Johnson will meet European Union (EU) leaders in June in a bid to reinvigorate stalled post-Brexit negotiations that London said Wednesday must finish by the end of 2020 even if no deal is reached.

Britain officially left the EU in January but still trades with other nations as if it were a member of the bloc.

London and Brussels must still agree on everything from fishing rights to state aid rules and environmental standards to avoid a chaotic breakup that might hurt workers and frighten financial markets.

They have given themselves until the end of 2020 to strike an agreement - and until June 30 to approve an extension to the talks if it seems like more time is required.

Johnson's chief negotiator David Frost reaffirmed to UK lawmakers on Wednesday that Britain had no intention of asking for more time despite fundamental differences in the sides' positions.

"The firm policy of the government is that we will not extend the transition period, and if asked, we will not agree to it," Frost told a video conference.

"I think that we will always put a lot of emphasis on economic and political freedom at the end of this year and thus avoiding ongoing significant payments into the EU budget."

Brexit dominated British politics and frustrated EU officials for years after the seismic 2016 EU membership referendum - won against the odds by the Brexit camp championed by Johnson.

But the coronavirus pandemic has put EU-UK talks on the back-burner. Frost and his EU counterpart Michel Barnier developed COVID-19 and Johnson himself was hospitalized for the virus in April.

The three have since recovered and the sides concluded a third round of video conference talks in May.

"We are perhaps a little bit behind where we would like to be otherwise, but only by a week or two," Frost said.

He said Johnson would join the talks before the June deadline for a summit that could determine whether Britain simply splits from the other 27 nations without a trade deal in 2021.

"The expectation on both sides is that these are done at leader level," Frost said.

The EU is willing to offer Britain preferential trade terms if Johnson signs up to the major standards and regulations followed by the remaining 27 nations of the bloc.

Barnier has sent a letter to UK parliamentary leaders reaffirming that Brussels was open to extending the talks for one or two years.

Debates about Britain's acceptance of the EU "level playing field" on standards and regulations are at the heart of the negotiations.

Johnson's team argues that the whole point of Brexit was to give Britain the right to set its own rules.

AFP