Greece is preparing for a final day of campaigning before Sunday's parliamentary election re-run brought about by last month's inconclusive vote.
The latest polls indicate that radical left-wing party Syriza, led by Alexis Tsipras, is tied with the Conservative New Democracy party.
Eurozone leaders are scheduled to hold a teleconference on Sunday following the election.
An official said the main concern was the risk of large capital outflows from Greece if depositors worry their savings in euros could later be frozen or converted into new drachmas, should the Syriza party win.
Mr Tsipras said the memorandum deal with Greece's international lenders would not last beyond the weekend.
Meanwhile, ECB President Mario Draghi has said the eurozone economy faces serious risks and politicians must act fast, although the European Central Bank stands ready to provide further liquidity to solvent banks.
No eurozone countries face an inflation risk, Mr Draghi added - just days after other ECB policymakers said the central bank might be open to cutting interest rates.
His comments come after other central banks from major economies said they stood ready to take steps, including coordinated action, to stabilise markets as world economies prepare for a possible financial storm or public panic after the elections in Greece.
Mr Draghi added, however, that inflation expectations remained well anchored and that "there is no inflation risk in any euro area country."
He said there had been a "string of negative survey data" since the 24 May cut-off period for the ECB's latest staff projections, which pointed to the economic situation stabilising.
Earlier, the German Chancellor warned that her country's financial strength should not be overestimated by those who believe German money can solve every problem.
Angela Merkel has also warned against overstraining the resources of Europe's biggest economy.
She rejected solutions to the eurozone debt crisis such as issuing joint euro bonds or creating a Europe-wide deposit guarantee scheme.
Ms Merkel said such proposals were "counter-productive" and would also violate the German constitution.
Merkel critical of France's economic performance
In a separate development, Ms Merkel has criticised France's economic performance in a war of words with its new Socialist President Francois Hollande over how to tackle Europe's deepening debt crisis.
Describing her own country as Europe's "stabilising anchor and growth engine", the centre-right chancellor told German business leaders that Europe should talk about the growing gap between the bloc's two biggest economies and traditional allies.
The unusual rhetoric comes after Mr Hollande met with German centre-left opposition leaders this week and unveiled economic reforms, including a partial lowering of the pension age, that Berlin fears will only deepen France's economic problems.