Greek lenders Eurobank and Alpha Bank say a planned merger to create the country's largest bank by assets could be put on hold because of debt-relief negotiations between the crisis-hit country and private creditors.

The banks said Monday that "an accurate timeline cannot be given" to complete the deal announced last August because of the negotiations, AP news agency reported.

The closely watched talks would see private holders of Greek bonds cancel half their debt and likely accept additional losses in a swap for bonds with a longer maturity.

Greece's finance ministry expressed surprise at the announcement, arguing that the negotiations had produced "nothing new or different" to factors already taken into account by both banks.