The EU will only agree to discuss this when it judges that enough progress has been made on the "separation issues" - the "divorce bill", expat citizens' rights and the Northern Ireland border - that have been the subject of negotiations so far. "We are calling for people to come out to Roslea on Saturday and send a message that we can not have a reinforcement of the border in Ireland", said Erne East Councillor Brian McCaffrey.
A European Commission spokeswoman said a press conference will be held after the leaders meet.
But if a deal is to be in place and approved before the March 2019 Brexit deadline, negotiators probably have less than a year, Tusk said.
Despite the appearance of good cheer on both sides, significant tensions appeared to remain embedded in the agreement over the divorce deal, which will not be finalized until the very end of the full Brexit negotiation.
"We want to work with them on that, and not against them".
"If #Brexit is happening (wish it wasn't) staying in single market & customs union is only sensible option".
May has got the deal that she needed-and the agreement that businesses were clamoring for. Amid off-and-on threats to oust her, failure to move talks along could have cost Mrs May her job, and brought more instability.
And in a concession that is exercising several leading Brexiteers, including Iain Duncan Smith, the draft reports that the United Kingdom has also "accepted the competence of the (European Court of Justice) in relation to the interpretation of the Withdrawal Treaty".
Foreign Secretary Boris Johnson has insisted any Brexit deal must stick to the spirit of the Leave campaign.
Also, no one should expect the Irish problem - whose roots go back centuries - to go away.
What happens to the border between Northern Ireland and the Republic of Ireland has been among the key sticking points in Brexit negotiations.
Furthermore, media reports overnight confirm May had "edged closer to a deal with the Democratic Unionist party over the Irish border", ahead of a deadline laid down by the European Union for Sunday night.