Combined support for Greece from the IMF and the European Union would be the best way to help the over-borrowed country deal with its debt crisis, OECD Secretary General Angel Gurria said on Sunday.

Greece, which is paying almost twice as much as Germany to refinance maturing debt, is pressing its European partners for a concrete standby package to help bring its borrowing costs down.

Aiming for a 4.0 percentage point fiscal adjustment to shrink its budget gap to 8.7 percent of GDP this year, Greece has said it may have to turn to the IMF if a European solution is not found to help it manage its debt mountain.

Europe must offer strong support to Greece after the stability program it presented. Markets will get the message, Greece will lower its borrowing cost and move on to implement the measures and reforms, OECD's Gurria told Kathimerini newspaper in an interview.

I consider the best way is a combination of support, funding and guarantees. In this combination I see the IMF as well, he told the paper.

European Union leaders are set to discuss a support mechanism for Greece when they meet in Brussels on March 25-26 and EU Commission President Jose Manuel Barroso has urged member states to agree a standby aid package Greece.

Aiming to shake EU member states into action and win German backing, Barroso has said the situation could not be allowed to go on for much longer.

Germany's Finance Minister Wolfgang Schaeuble said on Saturday only the most extreme circumstances could justify a bailout of a European Union state from within the union, and that any such aid would have to be delivered bilaterally.

(Greece) cannot get out of the crisis alone, despite the measures it has taken, nor does the euro zone have a rescue mechanism for a member state at this moment. I think what is needed is a combined support package, Gurria told the paper.

Greece is a member of the IMF, why not ask for help? Many countries have turned to the IMF, why not Greece?

(Reporting by George Georgiopoulos; Editing by Hans Peters)