ATHENS, Greece — The European Central Bank and national central banks should be part of a debt relief deal with near-bankrupt Greece's private sector creditors ahead of a pressing deadline early next week, the Greek Finance Minister said Thursday.

Evangelos Venizelos said the deal should also involve reducing the interest rates Greece pays its European partners and the International Monetary Fund for its first bailout agreed in May 2010.

The ECB and European central banks have so far been exempt from a cut in the value of their Greek debt portfolios, estimated at more than €50 billion ($65 billion), to the annoyance of private bondholders who face an overall loss of about 70 percent.

The agreement, Venizelos said, must be struck by Monday, when finance ministers from the 17 countries using the euro meet in Brussels — although the date could be "slightly adjusted."

"One of the major outstanding issues that must be solved ... is to secure the terms of participation of the official sector, that is our European partners and the IMF ... in the effort to reduce the Greek public debt," Venizelos said.

Venizelos told a meeting of Socialist party deputies that Greece's target of reducing its crushing debt to sustainable levels by 2020 "requires the completion of a parallel Official Sector Involvement" — beyond the €100 billion writedown all but concluded with private bondholders.

He added: "That means that the European Central Bank must be mobilized, that we must solve issues concerning national central banks, and we must resolve issues concerning the level of the interest rate" of the first, €110 billion ($144 billion) bailout that has been shielding Greece from bankruptcy for the past 20 months.

A European Union official said Greece needs about an extra €15 billion ($20 billion) to get its debt down to manageable levels, and the rest of the eurozone could have to make up the shortfall. The official spoke on condition of anonymity because of the sensitivity of the matter.

German Finance Minister Wolfgang Schaeuble said on n-tv television Thursday that he didn't see the need for "any extra contributions from the public sector; we're carrying everything anyway." He didn't address the issue of the €15 billion funding gap.

Athens is locked in tough talks on two fronts to ensure that it remains solvent, dodging the very real threat of a disorderly default — which could likely be followed by a Greek exit from the eurozone — when a big bond issue matures late next month.

On the one hand are the negotiations with banks, pension funds, hedge funds and other owners of devalued Greek government bonds, known as Private Sector Involvement. But the country's coalition government also has to placate its European partners and the IMF that are urging deeper austerity cuts to release rescue loans from a second package agreed last year — but not yet finalized.

"There were ups and downs in the PSI talks because we, in reality, we've been forced to take part in a double negotiation," Venizelos said.

All the negotiations must be concluded "in the next three or four days at the most," he added.

Venizelos said Prime Minister Lucas Papademos will discuss the situation on Friday with leaders of the three parties in his government.

Under pressure from rescue creditors, Greece is racing to push through a raft of tough reforms, involving the pension system, an overhaul of the public sector, and labor relations.

"As a country, we have reached the brink of official bankruptcy," government spokesman Pantelis Kapsis told private Mega television. "We have been borrowing for so many years and now we have our backs to the wall, so we have difficult decisions to make."

Leaders of Greece's unions and employers resumed talks on Thursday to slash labor costs in the private sector — following considerable reductions in state employee's incomes under previous austerity cuts taken to secure the first bailout.

The two sides said they had made progress but not yet reached an agreement after their three-hour meeting, and said they would inform the government and rescue creditors of their respective positions. The Labor Ministry has cautioned against "violent" private sector wage cuts, saying labor costs have already fallen 28 percent over the past three years and are expected to shrink another 7.6 percent in 2012.

Debt inspectors from the EU, IMF and ECB — know as the troika — are currently visiting Athens, and insist the cuts are needed to boost Greece's sluggish competitiveness. They met with Venizelos late Thursday.

The leader of Greece's Orthodox Church warned on Thursday that rising poverty could trigger a "social explosion" amid deep austerity and record-high unemployment, as the country enters a fifth year of recession.

"Homelessness and even hunger — phenomena seen during (World War Two) — have reached nightmare proportions," Archbishop Ieronymos wrote in a letter to Papademos.

"Patience among Greeks is running out, giving way to a sense of anger," he said. "The medicine we are taking has proved fatal for the nation. More painful, and more unjust measures are now set to follow along the same, hopeless course."

The Greek church has stepped up a charity drive this week, during a cold snap that left much of the country in subfreezing temperatures and a growing number of homeless people at risk.

Unemployment in Greece has surged to 19.2 percent, with the jobless rate for people under age 25 at 47.2 percent, according to figures for October from the EU statistics agency, Eurostat.

Derek Gatopoulos in Athens, Gabriele Steinhauser in Brussels and David McHugh in Frankfurt contributed to this report.