Greek prime minister Alexis Tsipras has said there must be a "viable" solution to his country's debt crisis as he arrived for last-ditch talks to prevent it crashing out of the euro.
The radical left-wing Syriza government has drawn up new proposals for tackling its vast debts in an attempt to persuade its creditors to extend access to vital bailout funds.
Arriving in Brussels ahead of a crunch meeting of leaders from the 19 eurozone countries, Mr Tsipras said Greece needed a solution which would allow it to return to economic growth.
"This is time for a substantial, viable solution that allows Greece to come back to growth within the eurozone with social justice," he said.
Standing alongside him, European Commission president Jean-Claude Juncker said there had been progress in recent days but added: "We are not there yet".
Greece has to reach a deal with its creditors before a June 30 deadline to repay a 1.6 billion euro (£1.1 billion) loan from the International Monetary Fund (IMF).
Syriza is presenting its proposals to the heads of the three creditors - the IMF, European Union and European Central Bank (ECB) - ahead of the main eurozone summit.
The head of Mr Juncker's cabinet, Martin Selmayr, said that the latest offer from Athens represented a "good basis for progress".
But in a sign that the process could be complicated, he described it as "eine Zangengeburt" - German for a forceps delivery.
Although the UK is not in the single currency zone, Whitehall has drawn up contingency plans for a possible Greek exit - "Grexit" - from the eurozone.
Chancellor George Osborne said last week: "We hope for the best but we now must be prepared for the worst."
Amid signs that Greeks were withdrawing increased sums from the country's banks, the ECB has provided emergency assistance to prevent the country's cash machines running dry.
But British tourists heading to the country have been advised to take euros with them.
Abta, the body which represents travel agents and tour operators, said: "Holidaymakers heading out to Greece this summer are advised to take some cash in euros with them as well as other payment methods (credit/debit cards) so that they are covered for all situations.
"We would also advise them, as we would with any destination, to take out travel insurance as soon as they book their holiday to provide protection should they need to cancel.
"We do not anticipate that there will be any need for tour operators to rebook their customers to a different destination.
"At present we have no indication that holidaymakers will be disrupted; however, as with all destination matters, we will continue to monitor the situation and work with our members on any developments.
"This is an unusual situation but the industry is experienced in handling unusual situations."