Euro zone leaders will tell Greece that time and patience are running out for its leftist-led government to implement agreed reforms to avert a looming cash crunch that could force it out of the single currency.
Greece has been kept from bankruptcy by two international bailouts but now risks running out of money within weeks if it does not receive more funds.
Greek banks reported the largest deposit withdrawals in a month, a sign savers are worried about the outlook for the country's finances and institutions.
Prime Minister Alexis Tsipras has requested a meeting tonight with the leaders of Germany, France and the main EU institutions on the sidelines of a Brussels summit to press for Greece to receive short-term funds to keep itself afloat.
German Chancellor Angela Merkel doused any expectation of a deal at the late-night session, saying decisions were up to the Eurogroup of finance ministers of the 19-nation euro area.
"I want to say: don't expect a solution, don't expect a breakthrough. It's not the right setting," she told reporters on arrival at the summit. "Decisions are made in the Eurogroup and that's how it will remain."
French President Francois Hollande said the message to Mr Tsipras would be that all sides must stick to their commitments.
"What shocks me is not that the Greek government is making an effort for the poor. What we ask of Greece is to make the richest people pay tax," he said.
Mr Tsipras did not mention his country's acute funding problems in a brief comment on arrival, saying only: "The EU needs more political initiatives that respect both democracy and its treaties so that we leave behind the crisis and move to growth."
Ms Merkel earlier told the German parliament in Berlin the crisis could only be resolved if Greece stuck to reform commitments it made when it agreed with the euro zone on a four-month extension of its bailout programme.
A political meeting of a small group of leaders could not be used to circumvent the formal agreement Greece concluded on 20 February with the Eurogroup, she told MPs.
"There remains a very tough way ahead," Ms Merkel said. Greece must understand that international aid brought with it an obligation "to reform its budget and work towards one day no longer needing help".
European Council President Donald Tusk, who will chair the summit, said he arranged a side-meeting with Mr Tsipras to take the heat out of exchanges around the table.
Two EU/IMF bailouts totalling €240 billion have kept Greece from bankruptcy since 2010 but its economy has shrunk by 25%, partly due to austerity measures imposed by the lenders. It risks running out of cash without more aid or permission to issue more short-term debt.
European Commission President Jean-Claude Juncker has been trying to build bridges between Mr Tsipras and Greece's creditors.
His exasperated tone suggested even Greece’s friends are losing patience with its belligerent rhetoric and procrastination.
EU sources said Greece had refused to provide any update on public finances or reform plans in a conference call of senior euro zone officials on Tuesday and had denied EU, IMF and European Central Bank experts access to government buildings in Athens, insisting all meetings take place in a hotel.
