Theresa May will for the first time come face-to-face with the European Union's chief Brexit negotiator amid a General Election campaign she is seeking to define by Britain's exit from the bloc.
The Prime Minister will host Michel Barnier and European Commission president Jean-Claude Juncker for a working dinner at Downing Street at 7pm on Wednesday.
It will be the first time Mrs May has met Mr Barnier since taking office and the outcome of the meeting could influence an election campaign in which she is asking voters to give her a mandate for exit talks to begin after the June 8 poll.
The meeting also comes ahead of Saturday's European Council summit, when leaders of the other 27 EU countries will discuss their draft guidelines for Mr Barnier to take into the negotiations.
The issue of a "divorce bill" of an estimated £50 billion could arise, given the Frenchman's insistence that the UK must "settle the accounts" before beginning talks on a future trade relationship with the EU.
He was backed in the guidelines set out by European Council president Donald Tusk last month, which rejected the UK's pleas for parallel trade and divorce talks, but said negotiations on a future deal could begin as early as the autumn if Britain pays its exit bill.
The guidelines also left open the possibility of transitional arrangements to cover any period between the expected Brexit date of March 29 2019 and the conclusion of a new trade agreement.
According to the Telegraph, the Government is considering the possibility of paying into the EU budget to secure access to the single market for British businesses during any transition period.
Mrs May's official spokesman said she will use the meeting to stress that Britain will approach the talks "in a constructive manner and with great goodwill".
A Commission spokesman said the trio would focus on the "process" of the two-year negotiations under Article 50.
But there could also be a tricky conversation over Gibraltar after its status was raised in the draft EU guidelines, which indicated that Spain would be given a veto over the British territory's participation in a future trade deal.
Its inclusion in the guidelines enraged some in the UK, with former Tory leader Lord Howard appearing to suggest Mrs May would be prepared to go to war over the Rock. Both sides agree on the need to lower tensions.
Mrs May's warning in her Article 50 notification letter that security co-operation could be weakened if the EU does not strike a deal with the UK could also come up.
The rights of EU nationals in the UK and British expats on the continent could also arise, given both sides' wish to guarantee their status as soon as possible.
Elsewhere, Foreign Secretary and leading Brexit campaigner Boris Johnson will address the Easter Banquet hosted by the Lord Mayor of the City of London, while Brexit Secretary David Davis will make a speech at the Prosperity UK conference in the capital.