Brexit talks face 'very big gap' as new round begins

Britain and the EU kick off a third round of Brexit talks today still sharply divided over what comes first -- London's future relationship with the bloc or the costly divorce settlement.

The European Union says there has to be "sufficient progress" in three key areas -- EU citizen rights, Northern Ireland's border and the exit bill -- before it will turn to post-Brexit arrangements, possibly beginning in October.

Britain says the two strands should be negotiated in parallel, arguing that progress on a free trade deal may even help resolve other sticky issues such as the future EU-UK border between Northern Ireland and the Republic.

That is a complete no-go for Brussels, with officials saying they expected little progress in bridging a "very big gap" at this week's talks.

They also blamed Britain for a "lack of substance" despite a flurry of position papers they said were strong on aspiration but short on detail.

EU chief negotiator Michel Barnier meanwhile listed on Twitter the EU's own negotiating documents, noting: "EU positions clear and transparent since day one."

Barnier meets his British counterpart David Davis late afternoon for a first exchange, followed by three days of talks and a joint press conference.

Both sides have repeatedly warned that the clock is ticking down to the March 2019 Brexit deadline and that they are the ones doing their best to make progress.

Davis said today this week's talks were all about "driving forward the technical discussions across all the issues."

"In order to do that, we'll require flexibility and imagination from both sides," he said.

"We're ready to roll up our sleeves and get down to work once more." Asked about the British approach, the European Commission refused to be drawn today.

"Let's have the negotiators do their negotiation... As for flexibility, we are working within the mandate given us by the European Council (of member states)," EU spokeswoman Lucia Caudet said.

The talks take place amid continued turmoil in Britain, with the opposition Labour Party over the weekend backing a "soft" Brexit whereby the country remains in the EU's customs union and single market for a transition period.

Prime Minister Theresa May has said she wants Britain unequivocally out of both but her position has been crippled since a June election gamble backfired and she lost her parliamentary majority.

May remains in office thanks to a deal with Northern Ireland's ultra-conservative Democratic Unionist Party which views the EU-member Republic with deep suspicion.