Brexit minister David Davis met EU negotiator Michel Barnier for a second round of talks 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,"
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."