French Economy Minister Christine Lagarde said on Friday that governments were looking at an increase in Europe's emergency rescue fund in the debt crisis as well as extending its scope to buy bonds directly on markets.

Lagarde said European finance ministers had to submit options to a European Council meeting in March and these could include whether European stabilization funds should be allowed to purchase sovereign debt on the secondary market.

"The increase in the European Financial Stability Facility (EFSF) is one option which we are looking at, of course," Lagarde told a news conference.

If a decision is taken to expand the fund, Lagarde said it would be necessary to put a precise figure on the increase so it could be approved by national parliaments.

Other senior European officials have been calling for an expansion of the fund, but a French government spokesman had said earlier this week that the fund was sufficient.

German Finance Minister Wolfgang Schaeuble said on Thursday the debate about boosting the size of the rescue fund was not realistic.

Worries about whether the EFSF is large enough focus on estimates that only around 250 billion euros ($333.55 billion) of the 440 billion fund are effectively available to euro zone countries because of a complex loan guarantee system.

Analysts say that will not be enough to rescue both Spain and Portugal if they bow to debt market pressure and seek aid.

Asked about how large any increase in the EFSF could be, Lagarde said: "It is very premature (to say). Ministers of economy and finance must submit their proposals to a European Council meeting in March."

"These considerations include a range of instruments. It is not only about coming up with a figure for the EFSF, it is about ... the European Stability Mechanism (ESM), the transition between one and the other, the way they are used ... and the possibility of acquiring bonds on the secondary market," Lagarde said.