Greece is determined to reject the EU's latest proposals on a default-saving loan deal, two senior ministers said Sunday, ahead of a crucial week for the struggling nation's reform talks.

"It was an aggressive move designed to terrorise the Greek government," Finance Minister Yanis Varoufakis told Proto Thema daily, declaring "this Greek government cannot be terrorised".

The European Commission last week presented Greece with a five-page list of proposals, including sales tax hikes and cuts in civil servants' salaries and pensions.

Greek Prime Minister Alexis Tsipras on Friday blasted the proposals as "absurd" and insisted Athens would not accept a deal unless it included a restructuring of the country's massive debt.

Speaking at a G7 summit in Germany on Sunday Commission President Jean-Claude Juncker said Tsipras had promised to present a list of alternative reforms by Thursday evening, but had failed to do so.

"I never received this alternative proposal," Juncker said.

Varoufakis called the EU's proposals "borderline insulting".

"We need reforms, debt restructuring and investment...if we don't have all three together, we will not sign," he said.

Ramping up tension, Athens this week withheld a 300-million-euro ($334-million) loan repayment to the International Monetary Fund, opting instead to group four scheduled tranches into a single payment at the end of the month.

This means that Greece must now find 1.6 billion euros in three weeks -- funds it is unlikely to muster without a deal with its EU-IMF creditors.

Greece's bailout agreement with the creditors expires at the end of June.

Should Greece miss its loan payments and default, many fear that this would set off a chain of events that could lead to a messy Greek exit from the euro.

Many within the ruling Syriza party, including a number of cabinet members, say the PM should call early elections rather than accept further austerity measures.

"I do not think there is much room for a positive deal with the creditors...they probably seek submission," the cabinet's chief eurosceptic, Energy Minister Panagiotis Lafazanis, told To Vima weekly.

"They want to smash the country socially and humilate the government," he said.

Tsipras has doggedly sought to surmount the technical talks on Greece's reforms by directly appealing to key European leaders for a political decision.

On Saturday, he spoke again by telephone to German Chancellor Angela Merkel and French President Francois Hollande, and the three leaders agreed to meet on Wednesday on the sidelines of an EU summit in Brussels, the state-run ANA agency reported.

But European Commission President Jean-Claude Juncker refused a request from Tsipras to talk on the phone on Saturday.

"I can confirm that there was a request for a call... No phone call today," a commission spokesperson said.