Brussels - Britain and the EU have vowed to get to the "heart of the matter" as they launched fresh Brexit negotiations, even as bitter infighting gripped the British government.
Brexit minister David Davis met EU negotiator Michel Barnier for a second round of talks on Monday ahead of Britain's historic withdrawal from the bloc, scheduled for March 2019.
But in London there was fresh turmoil as weakened Prime Minister Theresa May prepared to urge her warring ministers to end damaging leaks against each other over Brexit.
"Now it's time to get down to work and make this a successful negotiation," Davis told reporters as Barnier welcomed him to the headquarters of the European Commission.
During four days of talks the two sides hope to make progress on key issues surrounding Britain's withdrawal, including citizens' rights and its exit bill, so that negotiations can move on to discuss a future trade deal later this year.
"For us it's incredibly important we now make good progress, that we negotiate through this and identify the differences so we can deal with them and identify the similarities so that we can reinforce them," added Davis.
Barnier, who has repeatedly called on Britain to set out a full divorce strategy, said they needed to "examine and compare our respective positions in order to make good progress."
"We'll now delve into the heart of the matter," Barnier, a former French foreign minister and European Commissioner, told reporters.
Davis however stayed only a few hours before returning to Britain for parliamentary business, officials said. He will come back to Brussels on Thursday for more talks with Barnier and a news conference.
Photographs of the brief meeting showed grim-faced EU negotiators with large sheaves of paper across a table from a grinning, empty-handed British team.
The talks are the first full round of negotiations that formally began last month with a one-day session to agree on a timetable.
The EU has demonstrated increasing confidence in recent weeks, accusing Britain of dithering over whether it wants a "hard" or "soft" Brexit more than a year after the shock referendum that propelled May to power.
But May's minority government remains fragile one month after the snap June 8 election in which her Conservative Party lost its majority, leaving the EU wondering whether she can actually formulate a coherent Brexit policy.
Over the weekend British newspapers were full of reports of a civil war within her cabinet, with finance minister Philip Hammond in particular being targeted over allegations he was trying to derail Brexit.
May herself was set to call them to order on Tuesday, her spokesman said.
"Cabinet must be able to hold discussions of government policy in private and the Prime Minister will be reminding her colleagues of that at the Cabinet meeting," the spokesman said.
Hammond himself acknowledged that ministers were divided on other elements of Brexit.
"I think on many fronts it would be helpful if my colleagues - all of us - focused on the job in hand. This government is facing a ticking clock over the Brexit negotiations," Hammond said on Sunday.
With the government paralysed, London has opted for a spot of royal soft power, sending Prince William and his wife Kate on a "Brexit diplomacy tour" of Poland and Germany.
The couple arrived with their children George and Charlotte in Warsaw at the start of a five-day tour.
Brussels insists it will only start discussing the future relationship once there has been "sufficient progress" on the divorce - an estimated 100-billion-euro ($112 billion) exit bill, the rights of three million EU citizens living in the UK, and the border in Northern Ireland.
This week's talks are also set to address more detailed concerns such as Britain's future in Euratom, the EU's nuclear safety agency, and the role of the European Court of Justice, the EU's top court.
EU leaders are set to decide at a summit in October whether there is enough common ground to move on to trade talks.
Common ground was very much lacking last week after British foreign minister and leading Brexiteer Boris Johnson remarked that the EU could "go whistle" over its massive Brexit bill demand, drawing a rebuke from Barnier.
Johnson, who was in Brussels on Monday separately to meet his 27 EU colleagues, said he hoped the bloc would accept the "very fair and serious offer" Britain had made on the rights of EU citizens.
Hammond, one of Johnson's main cabinet rivals, said Sunday that Britain will take responsibility for the money it owes, but dismissed the 100-billion-euro figure as "ridiculous".
By Danny Kemp