The eurozone also still needs to decide on additional measures to bring Greece's debt down to 120 percent of economic output by 2020 — the target leaders defined when they tentatively agreed on more aid in October.
The current plan, which includes the euro130 billion bailout, the euro100 billion debt relief and the new austerity measures, would leave Athens debt close to 129 percent of economic output at the end of the decade. The International Monetary Fund and the eurozone believe such a high debt load would be unsustainable without outside assistance.
Meanwhile, Athens took the first concrete steps toward making sure that a small number of holdouts cannot scupper the debt relief deal it has negotiated with private investors.
The Greek parliament is expected to soon introduce so-called collective action clauses in its outstanding bond contracts. The CACs would force holdouts to participate in the planned bond swap as long as a majority of investors approve.
As a prelude to the debt swap, the European Central Bank has started exchanging its holdings of Greek government bonds for newly issued bonds of the same value, according to a eurozone official with knowledge of the matter. Those new bonds would not be retrofitted with CACs, protecting the ECB from being forced into the swap deal.
The ECB bought around euro55 billion ($72 billion) worth of Greek debt in 2010 as investors dumped the country's bonds and interest rates soared. But because bond prices were already low at the time, analysts estimate the ECB spent only around euro40 billion on its holdings.
The exchange, expected to be completed by Monday, does not address the issue of whether the ECB would forego the profits on its Greek bond purchases to help close the financing gap in the new bailout program.
Bank officials have said they could simply return any investment profits to national governments, which could then do what they wanted with the money.
Charlton reported from Paris. David McHugh in Frankfurt, Germany; Geir Moulson in Berlin; Michael Corder in The Hague, Netherlands; and Derek Gatopoulos in Athens, Greece, contributed to this report.