European decision makers need to be cautious and the euro zone strengthened before the area using the euro can be expanded, so as to avoid economic crises in the future, European Economic and Monetary Affairs Commissioner Olli Rehn said in an interview with a Finnish broadcaster.

"The euro zone's own ability to act must be much better before it can begin to expand significantly," Rehn said in an interview published on television channel MTV3's website on Friday.

The euro zone has been suffering from a sovereign debt crisis since spring 2010 and Greece, Portugal and Ireland have needed bailout packages.

"I am not naming any names or criticising anybody, but the fact that Greece could join the euro zone in 2001 was with hindsight and maybe already then a big mistake," Rehn said.

He said Latvia, Lithuania and Poland are potential new euro zone members. At present there are 17 euro zone members.

Reuters