A summit of all European Union members planned for Sunday has been cancelled as "very difficult" talks over a third bailout deal for Greece continue.
Eurozone finance ministers adjourned the talks last night and they have now resumed.
European Council president Donald Tusk said a meeting of Eurogroup leaders would go ahead at 14:00GMT and "last until we conclude talks on Greece".
Without a deal, it is feared Greece could crash out of the euro.
The BBC's Jonny Dymond in Brussels says that rarely have EU meetings been cancelled at such short notice and with such a terse announcement.
Marathon talks on Saturday had ended without agreement and Eurogroup leader Jeroen Dijsselbloem described negotiations as "very difficult".
"We have had an in-depth discussion of the Greek proposals, the issue of credibility and trust was discussed and also of course financial issues involved, but we haven't concluded our discussions," Mr Dijsselbloem told reporters.
"It is still very difficult but work is in progress."
Talks resumed at 09:00 GMT.
The heads of all 28 EU member states would have faced two scenarios this evening. Either talking about the political implications of a deal struck by the eurozone finance ministers with Greece or, if talks failed, managing the fallout and discussing the implications of a possible "Grexit".
So the cancellation of the summit could be interpreted in two different ways. The first - that talks are going so badly that there's no point in flying Europe's leaders in to discuss a deal that won't happen today.
But under those circumstances you'd expect leaders to gather for emergency talks. Which is why some here interpret the cancellation as a positive sign; it implies that, while a deal is still a long way off, the will to strike that deal - today - is there, even if the negotiations have been slow, painful and at times bad-tempered.
The ministers have reportedly discussed in detail the option of easing Greece's debt burden as long as Athens enacts legislation immediately to reform taxation, pensions and administration. There will be no write-down of debt.
But the talks remain complex and European Commission Vice President Valdis Dombrovskis said it was "utterly unlikely" a mandate would be achieved in Sunday's meeting to start formal negotiations on the third bailout.
Slovakian Finance Minister Peter Kazimir was similarly downbeat, saying: "It's not possible to reach a deal today. We can agree on certain recommendations for the heads of state. That's all. The breach of trust... it's so big, it's not possible to achieve the deal."
Finnish Finance Minister Alexander Stubb said he was "still hopeful" of a deal but that on a scale of one to 10, Greece and its eurozone partners were "somewhere between three and four" on achieving a deal.