José Manuel Barroso has told politicians to stop “waiting for an accident” to happen with Greece and to work to avoid the country leaving the eurozone.
Formerly the head of the European Commission, Mr Barroso accused politicians of having taken “too long” to find a solution. Greece must find €304 million to repay the International Monetary Fund by 5 June.
Markets are jittery that Greece could default on its debt. Thousands of Greek savers have withdrawn their money from Greek banks, which has not helped the economy.
Mr Barroso said: "It will certainly be negative for Greece and the euro area if there is a default or if there is a Grexit. But I believe that a solution can still be found."
Previously he had expressed his concern that a Greek exit could kick start the disintegration of the euro.
Talks are scheduled for Sunday night between the Greek prime minister, the German Chancellor and the French president.
The Greek minister of the economy has given reassurances that Greece will meet the 5 June repayment.
Signals have come from other ministers that the country is ready to compromise in order to receive a lifeline of fresh low interest loans to replace debt.
Yanis Varoufakis, Greece's finance minister, said the government wanted a “combination of debt restructuring, investment injections and reforms that go beyond the inhumane practice of cutting pensions, benefits and wages".
