The remaining 27 EU states have unanimously agreed their strategy for Brexit talks.
European Council president Donald Tusk said the agreed guidelines give the member states a "firm and fair political mandate" for discussions with Britain over its exit from the EU.
The 27 leaders, who are meeting at a summit in Brussels, took less than 15 minutes to endorse draft guidelines which were issued on 31 March .
Under the terms of the EU strategy, Britain must settle its so-called divorce bill and reach agreement on the rights of EU citizens living in the UK before negotiations can move forward to trade talks.
This puts the EU on a collision course with No 10, as Theresa May has said she wants to negotiate a new trade deal with Europe alongside the divorce settlement.
The EU strategy also states that the Prime Minister has to reach an agreement on the Irish border and provide clarity over EU law in the UK within the withdrawal phase.
During the summit, it is understood that a commitment will be given that if Northern Ireland ever breaks away from the UK, the united Ireland would become an automatic member of the EU.
European Commission President Jean-Claude Juncker described the strategy agreement between EU leaders as "unity in action".
Earlier, Germany's finance minister warned that Britain will not have advantages over remaining member states after negotiations conclude.
Wolfgang Schaeuble said: "There is no free lunch. Britons must know that.
"We don't want to weaken Britain. But we also don't want that the rest of Europe is weakened.
"Britain should not have advantages after the exit, that other countries don't have."
The summit comes days after Mrs May hosted Mr Juncker and the Commission's Brexit negotiator Michel Barnier at No 10 for dinner.
The following morning, Chancellor Angela Merkel spoke with Mr Juncker and claimed that "some in Great Britain still have illusions" about the Brexit deal and the process of reaching it.
Addressing the German parliament, Mrs Merkel said: "Countries with a third country status - and that's what Great Britain will be - cannot and will not have the same or even more rights as a member of the European Union.
"You may think that all this is self-evident. But I have to put this so clearly because I get the impression that some in Great Britain still have illusions about this and that is a waste of time."
Brexit talks are expected to begin after the General Election on 8 June.