"It is quite clear that there is an evident risk that the Greek programme is off track," Anders Borg told reporters as he arrived for a meeting of European Union finance ministers.
The Greek debt crisis tops the agenda at the meeting of the Economic and Financial Affairs Council (Ecofin) meeting of EU finance ministers.
"With a debt level of 160-170 of GDP there is a significant risk that it falls off the rails," Borg said of Greece's latest budget forecasts for 2011-2012.
Borg called for action to ensure that the situation is managed effectively.
"We have to rethink how we can move faster forward towards backstops and firewalls to handle the situation," he said amid fears Greece is heading towards a default that could devastate the eurozone.
He said banks may have to be recapitalised to cope with the crisis and underlined the importance of having funds available if a move of this kind would become necessary.
The day before, eurozone finance ministers put off a decision on releasing the next installment of bailout funds to Greece, saying Athens can wait until November.