The Greek government's junior coalition partner has said it cannot back the agreement announced between Greece and its European creditors, describing the proposed deal as a German-led "coup".

Defence Minister Panos Kammenos, leader of the right-wing Independent Greeks party, said on Monday he had no plans to leave the government but added he would not join a national unity government, the Associated Press news agency reported.

"The prime minister of this country was faced with a coup staged by Germany and other countries," Kammenos said after meeting with Prime Minister Alexis Tsipras, adding "this deal introduced many new issues ... we cannot agree with it."

The announcement is a blow to Tsipras' six-month-old government, which is struggling to maintain its majority in parliament, ahead of Tuesday's vote on the reforms needed to unlock the eurozone rescue deal.

Civil servant strike

Al Jazeera's John Psaropoulos, reporting from Athens, said that the Greek government would have to take tough measures to meet the requirements of the deal, but Tsipras would "put the best possible spin on all of this".

He said the fact that the government would have to sell some of the state property to generate 50bn Euros as part of the deal would face resistance from the Greek people.

"He is going to say: "Look, we've got through the most difficult negotiations that Greece ever had to face so far. And what we've come away with is at least a promise to look at the rescheduling of debt. It was never on the table before, now it is", he said.

Tsipras faces added pressure from Greece's public servants, who are being called to stage a 24-hour strike on Wednesday.

Their union, Adedy, called for the stoppage in a statement issued on Monday, saying it was to show their opposition to the outline agreement with the eurozone.

It will also urge the civil servants to take part in a demonstration against the reforms scheduled to take place in front of parliament late Wednesday.

This will be the first strike to happen under Tsipras, the head of the left-wing Syriza bloc.

Before coming to power, Syriza participated in stoppages and demonstrations against austerity in 2010 and 2014, which previous conservative governments voted for.

Demonstrations were already to take place in Athens late Monday against the latest reform package, which requires parliament to back tax hikes and pension cuts in return for the eurozone bailout worth up to $96 billion, and against the euro.

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Without the loan, Greece's economy is likely to shatter, with exit from the euro a very real possibility.

To secure the rescue, Tsipras is going to have to win parliamentary backing, maybe relying on opposition votes if many of his Syriza MPs rebel.

Syriza and its junior coalition partner, the Independent Greeks, are to hold separate meetings on Tuesday to study the reform package.