David Davis has pledged to "work intensively" with his counterpart Michel Barnier in order to reach an agreement on transition by the hoped-for deadline of March.
The Brexit secretary hosted a meeting and lunch with his EU counterpart in Downing Street today, with Prime Minister Theresa May meeting the pair in what an official spokesman described as "an opportunity to take stock".
Davis tweeted this afternoon that he and Barnier had had "constructive talks today", adding: "Our teams will work intensively to agree an implementation period by March."
Barnier stressed "the time has come" for the UK to make a choice on whether to be part of the customs union, adding "being outside means there will be unavoidable barriers to trade".
The meeting comes ahead of a two-day Cabinet war committee, in which it is hoped the government will finally agree what it wants from an end state.
Exactly what that means in reference to the customs union has come under the microscope in recent days, with a Number 10 spokesman this morning saying the two options on the table "are a highly-streamlined customs arrangement and a new customs partnership with the EU".
Assuming a position can be agreed between the fractured - and fractious - Cabinet, senior civil servant Olly Robbins will be heading to Brussels to progress discussions that have been going on behind the scenes since sufficient progress was agreed mid-December.