A final communique stipulates that European Union leaders will give Britain until May 22 to leave if the UK Parliament backs May's Brexit deal next week.
If the Prime Minister fails in doing what she is told by European leaders, the United Kingdom will either leave - against the wishes of nearly everyone in the British and European political establishments - without a deal, or remain an EU member for either the long or short term.
"What this means in practice is that, until that date, all options will remain open, and the cliff-edge date will be delayed", he said.
The former prime minister was questioned by the ambassadors on whether such a referendum could heal the UK's divisions or simply prolong the country's agony.
To get more time to get lawmakers on her side, and to allow for the technical details of the deal through Parliament, she traveled to Brussels with a request of a delay until June 30.
23 May: European Parliament elections take place across the EU, with or without the UK. In this second scenario, the EU27 expect the United Kingdom to indicate a path forward before the April deadline. If Parliament does not agree a deal next week, the EU Council will extend Article 50 until 12 April.
Friday 29 March: This is no longer due to be the official Brexit date unless something drastic happens in the next few days that prevents the dates being changed in legislature.
European Union leaders wanted to avoid being put under pressure next week in case the deal is once again rejected in Westminster, leaving little time for the European Union to avoid a no-deal scenario and be blamed for a disorderly Brexit.
"National humiliation is imminent through these "indicative votes", said Conservative MP Steve Baker, who favours leaving without a deal.
Between 80,000 and 100,000 people have been simultaneously viewing the petition to revoke article 50.
The Labour deputy will tell supporters: "Brexit is now stuck in the pipework of Parliament, with MPs split, completely unable to agree or find a way forward".
An online petition asking the British government to revoke Brexit briefly crashed on Thursday after a surge in support saw it garner more than 600,000 signatures in less than 24 hours.
Meanwhile, May has asked the other EU countries for a three-month extension to Brexit, until just before the newly-elected European Parliament starts work at the beginning of July.