After months of denial, Spanish Prime Minister Mariano Rajoy is hinting for the first time that his debt-ridden country may seek an international bailout.

Before deciding, Mr. Rajoy said he would first study how the European Central Bank structures its new plan to buy government bonds of debtor nations, including Spain and Italy. The bank's direct bond purchases could cut the soaring borrowing costs Madrid and Rome are facing on the world's financial markets.

The interest rates on Madrid's bonds have spiraled to the level that forced Greece, Ireland and Portugal to seek rescue packages. Until now, Spanish officials had denied the government's need for a bailout.

But at his traditional mid-year news conference, Mr. Rajoy said that once he knows more about the central bank's bond purchase plan, he would “take the best decision” for Spain on a bailout.