An accord by the end of the week is "possible but it's not yet certain," Belgian Prime Minister Charles Michel said as he arrived for an emergency euro-area summit in Brussels. German Chancellor Angela Merkel was even less committal, saying the leaders' meeting would be consultative only since as yet there was "no basis for a decision."

Greek stocks and bonds surged on Monday after Tsipras's government submitted new proposals addressing the areas of pensions, sales taxes and fiscal targets that had proven the chief barriers to a deal. That optimism was toned down by leaders amid disagreements over the fine print, including on Greek demands for some form of debt relief.

With the clock ticking toward a June 30 deadline both for the expiry of the European portion of Greece's bailout and payments to the International Monetary Fund, leaders stressed the work still to do in the tiime available.