The leaders of the other 27 European Union member-states are to meet in Brussels to discuss the plan for handling the Brexit talks - without the UK.
The discussion, to take place after Theresa May leaves a summit meeting of all EU leaders, is reportedly to confirm Michel Barnier's receipt of the lead role for the EU in the negotiations.
The meeting is also expected to decide how the EU will organise itself for the negotiations following the formal triggering of Article 50.
Number 10 welcomed this development, claiming it showed the EU recognised the UK would be leaving as promised.
A spokesperson said: "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."
But there could be further issues, as MEPs claimed the leaders' plan - which was seen in a leaked draft - sidelined Guy Verhofstadt, who has been asked to lead the negotiations for the European Parliament.
The former Belgian prime minister said: "If the government leaders don't take the European Parliament's role seriously, we'll negotiate directly with the British.
"If that's what they want, they'll get it."