"The ECB has done a major service for short term market stabilization," Rehn told Reuters in an interview, calling the ECB's decision "an essential element of crisis response of the euro area."

ECB President Mario Draghi unveiled plans on Thursday for potentially unlimited purchases of bonds of up to three years maturity issued by countries that request a European bailout and fulfill strict domestic policy conditions.

Rehn said the policy conditions would be based on existing country-specific recommendations and "would have to include very specific objectives and a time line on how to meet the objectives."

No countries have yet applied for help from the yield reduction plan, he said.

(Reporting by Francesca Landini and Lisa Jucca, writing by Gavin Jones)

• A Permanent Economic Emergency