People walk past the Bank of Greece in Athens May 9, 2011. [Photo/Agencies]

ATHENS - Greece should complete talks by the end of the week with inspectors from the EU and IMF on a medium-term budget plan plus a vital next slice of international aid, sources close to the negotiations said on Wednesday.

With Athens fighting to avoid defaulting on its debt, the country's central bank chief dismissed as "improbable and ridiculous" any suggestion that Greece might ditch the euro and return to its drachma national currency.

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Inspectors on the "troika" team from the European Union, IMF and European Central Bank are in Athens to decide whether to release a tranche of 12 billion euros next month to keep Greece afloat. Partly due to IMF demands, discussions on a new package that would meet Greece's needs up to 2014 are also taking place.

Asked when the review would be concluded, one source said: "Tomorrow if we are lucky, but it could also be Friday."

A German finance ministry spokesman said Berlin expected the Troika to report on Friday evening at the earliest and that Germany expected the European Union and the International Monetary Fund to remain involved jointly in any continued aid program for Greece.

Sources said that whether Athens gets the fifth tranche of aid under its existing 110 billion euros EU/IMF bailout will depend on senior EU finance officials who are gathered in Vienna and on euro zone finance ministers, who may meet earlier than their next scheduled talks on June 20.

European officials are holding talks in the Austrian capital to sketch out options for a second bailout package, with private sector participation still under discussion to help relieve the country of its massive debt burden.

A Greek source with knowledge of the Athens negotiations was optimistic that Greece would get the latest slice of money to cover its budget deficit and meet debt repayments.

"There will be a way for the disbursement of the fifth installment to be approved," he told Reuters. "The negotiations with the troika will be concluded today or tomorrow, the latest by Friday. The new assessment will include measures to speed up privatizations, to cut spending and increase revenues."

A new package for Greece, expected to total around 65 billion euros according to EU officials, could involve a mixture of collateralized loans from the EU and International Monetary Fund, and additional revenue measures.

It would involve unprecedented intrusive external supervision of the privatization program, which has yet to sell anything since the rescue a year ago.

Deputy Greek Prime Minister Theodoros Pangalos will chair a ministerial meeting on Wednesday on moves to shrink the public sector as Athens scrambles to cut its wage bill further.