European Union's chief Brexit negotiator Michel Barnier and his delegation and Britain's Secretary of State for Exiting the European Union David Davis and his delegation attend a first full round of talks on Britain's divorce terms from the European Union, in Brussels, Belgium, July 17, 2017.
"We'll now delve into the heart of the matter", Barnier told reporters, declining questions until the end of this round of talks on Thursday.
Barnier and Davis last month agreed on a potential timetable for negotiations towards a future trade relationship, which Britain would like to start as soon as possible.
There was little let-up on Monday, with the Telegraph citing an unidentified cabinet minister as accusing Hammond of trying to frustrate Brexit, and treating pro-leave colleagues as if they were pirates who had kidnapped him.
Barnier, a former French cabinet minister who was flanked at the table by his German deputy Sabine Weyand and French strategy chief Stephanie Riso, has urged the British to give more detail on what they want, more than a year after they voted for Brexit.
He pointed to four categories where they needed to make progress on: "The issue of citizens' rights, the issue of finance, of separation and of course, separately, Northern Ireland".
One key early advance that European Union officials hope for this week is for Britain to stop challenging the principle it will owe Brussels money - though how much will have to be argued over and can not be calculated until Britain actually leaves.
Video Davis Let's get down to business
Prime Minister Theresa May, her authority diminished after losing her majority in a June election she did not need to call, has struggled to control rival cabinet ministers.
"I don't see these great divisions that are suggested to me in the Sunday newspapers and I have to say I think all of this is somewhat overplayed", he told BBC Radio 4's Today programme.
Earlier estimates put the bill between €60 billion and €100 billion.
It said Britain's plan "would cast a dark cloud of vagueness and uncertainty over millions of Europeans" by giving EU citizens living in Britain fewer rights than those of British citizens in the EU.
More divisions were exposed last Sunday, when Hammond said transitional arrangements for Britain leaving the European Union are likely to last a couple of years, rather than the few months suggested by Trade Secretary Liam Fox.
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