The UK's new Brexit secretary will hold his first talks with the EU's chief negotiator in Brussels later.
Dominic Raab was appointed when David Davis resigned in protest at Theresa May's plans for post-Brexit trade.
It now falls to Mr Raab - part of the winning Leave campaign in the 2016 EU referendum - to continue negotiations with the EU's Michel Barnier.
Their meeting comes as the European Commission is instructing other EU states to prepare for a no-deal Brexit.
The BBC has seen a draft of a commission paper which warns that failure to reach a deal would have a considerable impact on European business and citizens.
Possible consequences, the paper says, include disruption to the aviation industry and goods from the UK being subject to custom checks.
Taoiseach (Irish prime minister) Leo Varadkar has said his government is making contingency plans for "the unlikely event of a no-deal hard Brexit".
Mr Varadkar said that - even if there is a deal - Ireland will need 1,000 new customs officers and veterinary inspectors to deal with changes in trade rules with the UK.
In the UK, the government has advised all its departments to have fully planned contingencies in place in the event of the UK withdrawing from the EU without an agreement.
However the government watchdog, the National Audit Office, has warned that, in the case of one department, there is "still much to do".
On Thursday, Theresa May will be making her first visit to the Irish border since the Brexit referendum.
No 10 says the visit will "reaffirm her commitment to a Brexit that avoids a hard border and protects the Belfast Agreement".
The UK is due to leave the EU on 29 March 2019.
But the two sides have yet to agree how their final relationship will work, with key issues around cross-border trade unresolved.
Mr Raab's trip to Brussels comes with debate raging within the Conservative Party about what Brexit should look like.