A technical team stayed in the Greek capital to work on details, and negotiations will continue over the phone, but it is unlikely a deal can be clinched before a crucial meeting on Monday of euro zone finance ministers, the sources said.

Greek officials had been expecting Institute of International Finance chief Charles Dallara, who negotiates in the name of creditors, to hold meetings on Saturday but he left early in the day for Paris.

The IIF denied that Dallara and his adviser Jean Lemierre had left unexpectedly and said they had longstanding personal appointments.

Following several rounds of talks from Wednesday to Friday, Greece and its private creditors are converging towards a deal in which private creditors will take a real loss of 65 to 70 percent, sources close to the negotiations said.

But a lot of details are still unresolved, including on legal aspects of the deal, the sources said.

"Discussions will continue over the phone this weekend but an agreement is unlikely before next week, if there is an agreement at all," one source close to the talks said. "Things are complicated, we are getting closer on the numbers but there is still quite some work ahead."

Much of the attention will now turn to the euro zone finance ministers' meeting in Brussels, and to how EU paymaster Germany and the IMF view the progress in the debt swap talks.

The IMF and EU countries, and in particular the bloc's paymaster Germany, want to make sure the deal puts Greece's derailed finances back on a sustainable track before they agree to a new, 130 billion-euro ($168.2 billion) bailout, which is also crucial to avoid a messy default. How much money Athens needs from official lenders also depends on the details of the debt swap deal.

The IMF insists any deal must ensure Greece's debt burden will be cut to 120 percent of GDP by 2020 from 160 percent now, as agreed at an EU summit in October, and has warned that this is made more difficult by the fact that Athens' economic prospects have deteriorated since.

The IIF repeated on Saturday that progress was made and the talks were continuing. "They (Dallara and Lemierre) are both fully available to the Greek government's leadership by telephone should this be necessary," the IIF said in a statement.

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For a Breakingviews calculator on Greek bondholders: here

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DEBT SUSTAINABILITY

A new analysis of Greece's debt sustainability could be ready before euro zone finance ministers discuss the debt swap plan on Monday, or by mid-week, a senior EU told Reuters, adding that a lot depended on how that was calculated.

"We will want to test the waters among member states because, given the complex connections between private sector and official funding elements, we have to have the backing of member states for a deal," a senior EU source told Reuters, referring to the Eurogroup meeting.

Long-term projections for Greece's economy, now in its fifth year of recession, will be key.

Haggling over the coupon had held up the long-running talks as Greece raced to wrap up an agreement, raising the prospect of a messy default when Athens faces 14.5 billion euros ($18.5 billion) of bond repayments in March.

Sources close to the talks said the new bonds would likely feature 30-year maturity and a progressive interest rate averaging out at 4 percent, a banking official close to the talks told Reuters.

A 15 percent cash sweetener will be made up of short-term bonds from Europe's temporary bailout fund, the European Financial Stability Facility (EFSF), two sources told Reuters.

"It will be near cash-equivalent short-term EFSF bonds," one of the sources said.

"The euro zone ministers will examine the proposal and say whether we have a deal. If they say we don't, we're back to the negotiating table," a banking source close to the talks said.

(Additional reporting by Paul Taylor, Steve Slater, Ed Taylor, Lefteris Papadimas and George Georgiopoulos; Writing by Ingrid Melander; Editing by Alison Birrane)

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