Leaders of the 27 other European Union countries are set to meet in Brussels to discuss their plans for handling the Brexit talks.
The discussion will take place after British Prime Minister Theresa May has left the summit meeting of all EU leaders.
The talks, which are expected to take place over dinner, will decide how the EU will organise itself for the talks which will follow Mrs May triggering Article 50, the formal legal mechanism which officially begins the two-year countdown to Brexit.
The meeting is expected to see the European Commission's top Brexit official Michel Barnier given the lead role in the negotiations.
British sources welcomed the talks, saying they showed that the EU recognised that the UK would be leaving the bloc as promised by the Prime Minister.
"It shows that they are facing up to the reality that the UK is leaving the EU, that we are going to be triggering Article 50 by the end of March, that means they are going to need to know how they are going to handle the process where they have got to work out the position of 27," a Number 10 source said.
Mrs May will hold talks with the outgoing president of the European Parliament Martin Schulz in the margins of the Brussels summit.
She will also meet Latvian prime minister Maris Kucinskis and Lithuanian president Dalia Grybauskaite, meaning that she will have held talks with leaders from all EU countries apart from Austria and Bulgaria by the time the summit starts.