Greece's newly-appointed Prime Minister Alexis Tsipras (C) leaves the Presidential Mansion after his swearing-in ceremony as Greece's first leftist prime minister in Athens January 26, 2015. [Photo/Agencies]

Irish Finance Minister Michael Noonan said there could be some room for a deal to adjust debt maturities and cut interest rates rather than writing the debt off.

But Tsipras can expect strong resistance to his demands from Germany in particular and a series of European policymakers urged Syriza not to renege on previous governments' commitments.

"There is no room for unilateral action in Europe," ECB Executive Board member Benoit Coeure told Europe 1 radio, saying it was important to play by the "European rules of the game".

Tsipras has drawn the ire of lenders with his pledge to end budget cuts and heavy tax rises that have helped send the jobless rate over 25 percent and pushed millions into poverty.

But with Greece unable to tap the markets because of sky-high borrowing costs and facing about 10 billion euros of debt payments this summer, he may find himself with limited room to fight creditors. The new prime minister will also need a deal to unlock more than 7 billion euros of outstanding aid to make debt payments in the summer.

Standard and Poor's sent an early warning shot to Greece's new government, saying it could downgrade its credit rating even before its next planned review in mid-March if things go badly.