"There will be no showdown between our government and the European Union. There will be no threats, it's not about who climbs down first," said new Finance Minister Yanis Varoufakis.
Prime Minister Alexis Tsipras earlier told his cabinet that Greece would seek a "fair, mutually beneficial solution" with its EU peers to renegotiate its 240 billion euro (USD 269 billion) EU-IMF bailout and make its huge debt socially manageable.
In a speech to the cabinet -- his first since taking office -- the 40-year-old premier however insisted that Greece's new leaders were no longer willing to bow to the "politics of submission", in a clear swipe at Brussels and the International Monetary Fund.
But the new government's radical anti-austerity agenda has alarmed financial markets, reviving fears that Greece could crash out of the eurozone.
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Greek stocks were shedding over 7.0 per cent in late afternoon trade -- after losing 3 per cent the previous day -- and yields on 10-year bonds also rose above the symbolic barrier of 10 per cent.
And in another move that spooked markets, the government halted the privatisation of Greece's main port, Piraeus, which Chinese shipping giant COSCO had planned to turn into its new European hub.
Varoufakis, a fierce critic of the conditions imposed by creditors, today called the cuts "a toxic mistake...That took a toll in human lives, either lost or undermined."
The ruling Syriza party has made frequent references to a "New Deal", harking back to the stimulus programme that pulled the United States out of the Great Depression in the 1930s.
The new coalition -- which has 162 seats in the 300-member parliament -- must address an end-of-February deadline set by the EU for Greece to carry out more reforms in return for a seven billion euro tranche of financial aid from the bloc and the IMF.