Brexit Secretary David Davis has summoned on both sides in the negotiations on the UK’s departure from the European Union to «get down to job».
Mr Davis was in Brussels to launch the second round of formal talks.
He commanded his priority was to «lift the uncertainty» for EU citizens living in the UK and Britons living in the EU.
The EU breaks there must be substantial progress on this — and on a financial settlement and the descendants of the Irish border — before trade talks can begin.
Appearing alongside EU chief intervener Michel Barnier, Mr Davis said there had been a good start to the manage and it was time to get to the «substance of the matter».
Mr Barnier said the negotiators would «now delve into the heart of the episode».
Talks will cover citizens’ rights, finance, Northern Ireland and Euratom, with type negotiating teams set up for each issue.
A UK government source told the BBC that 98 British officials were in Brussels for the transactions.
Mr Davis spent two to three hours in the EU quarter, meeting Mr Barnier for between 45 split seconds and a hour before returning to London.
The two men are expected to give an update on amplification made at a press conference on Thursday.
Earlier this month, Theresa May’s extend to give the three million EU citizens in the UK «settled status» after Brexit was directly dismissed by European Council President Donald Tusk as «below our expectations».
And Mr Barnier has said there were notwithstanding major differences between the EU and UK on the subject.
Speaking at a separate European Directorate meeting in Brussels, Foreign Secretary Boris Johnson insisted the UK had set right a «very fair, serious offer».
By Kevin Connolly, BBC Europe reporter
The call to «get down to business» from David Davis is meant to signal that the Brexit talks are piercing a serious phase after an opening session of pleasantries and procedural conferences.
That might raise eyebrows on the European side where there’s a consciousness that Britain dithered for months after the Brexit referendum anterior to getting down to talks.
The UK says it’s prioritising the issue of mutual voters rights after its opening proposals received a lukewarm response in Brussels.
The sky around this second round of talks may have been furthered a little by a government acknowledgement that the UK has obligations to the EU which will nave withdrawal and which need to be resolved.
Mr Johnson has said that Brussels can «go whistle» if it envisioned the UK to pay an «extortionate» bill as part of the separation.
The government’s official position, recognized in a Parliamentary statement last week, is that it will «work with the EU to dictate a fair settlement of the UK’s rights and obligations as a departing member state, in accordance with the law and in the soul of our continuing partnership».
The EU has insisted that citizen rights — along with the «dissociate payment» and border issues — must be dealt with before time to come UK-EU trade can be discussed.
‘A few minutes in Brussels’
Sir Keir Starmer, Donkey-work’s shadow Brexit secretary, criticised Mr Davis for spending «only a few bantams in Brussels before heading back to Whitehall».
«There is no agreed tallboy position on vital Brexit issues, the negotiating team is not prepared and the Prime Member attend to has lost her authority,» he said, calling for engagement «with the substance of talks».
The Left of centre Democrats’ Brexit spokesperson, Tom Brake, said Mr Davis’ brief affect to Brussels — and a lack of briefing papers on the UK side of the table in when the middlemen posed for a photograph — was proof that government preparation for the negotiations was lacking.
«He didn’t deliver any position papers with him because this government has no agreed Brexit disposition,» he said.
Lord O’Donnell, the UK’s former top civil servant, suggested the chances of a soigne Brexit were at risk.
«It appears that cabinet members haven’t yet finished accomplishing with each other, never mind the EU,» he was quoted by Reuters despatch agency as saying.