But the point was effectively conceded before talks began, with Mr Davis yesterday accepting an European Union timetable set out last week, which makes clear trade will only be discussed once "sufficient progress" is made on citizenship, Northern Ireland and a "single financial settlement" of as much as £88 billion.
Davis will lead a team of experienced negotiators to Brussels, confident that he can get a positive outcome and secure a new deep and special partnership with the European Union, said his spokesman.
Outlining its official position last month, the European Union said it needed detailed guarantees so citizens have the same rights to work, pensions, education and healthcare - so they can live "as if Brexit never happened", in the words of one senior official.
The U.K. and the European Union started talks on Britain's exit from the bloc Monday morning, nearly a year after the U.K. voted to leave, with EU chief negotiator saying he hoped the two sides can start removing the uncertainties created by that decision.
He hailed that the the first session was "important", "open", and "useful indeed to start off on the right foot as the clock is ticking".
More broadly, Brexit talks will have to address a range of regulatory issues, including laws about worker rights, climate and agriculture.
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"In a first step, we will deal with the most pressing issues". We must lift the uncertainty caused by Brexit.
"And use the time in between to work on proposals and exchange them".
The two sides agreed to set up three working groups covering the details of withdrawal: the financial settlement; citizens' rights; and one dealing with other legal issues relating to "separation". "There is a long, long way to go for negotiations". The government said that it is seeking an agreement "like no other in history" even as the country had got into hard negotiation terms over the issue.
British Prime Minister Theresa May is due to praise the good atmosphere at Monday's Brexit talks, and explain how to protect the rights of citizens hit by Britain's departure. If its assessment is positive, the talks will then move on to "scoping the future relationship on trade and other matters".
"It's not when it starts it's how it finishes that matters", he said.
Since the British election, French President Emmanuel Macron and German Foreign Minister Sigmar Gabriel have said they would welcome Britain back if it reversed its decision to leave the union.
Merkel said Monday: "I think it is premature to speculate on the first day of the negotiations how they will end". "It's not about punishment, it is not about revenge", Barnier said.