PARIS — Spain paid a sharply higher interest rate on an auction of long-term bonds Thursday and a new strike hit Greece, illustrating the pressures on European leaders heading into a summit meeting to find a solution to the bloc’s debt problems.

The two-day meeting, which begins Thursday night in Brussels, was expected to produce agreement on the outline of a permanent bailout fund for euro zone countries in financial trouble. But important details, such as its size and scope, will likely be left until the spring.

Disagreements between Chancellor Angela Merkel of Germany, the euro zone’s biggest member, and Jean-Claude Juncker of Luxembourg, who heads the group of 16 euro zone finance ministers, could slow progress toward a united response to market “attacks” on the bonds of weak members. Greece and Ireland have already sought aid from the European Union and International Monetary Fund, and Portugal, Spain and others are seen as vulnerable.

Mrs. Merkel has resisted efforts to create common bonds for the euro zone, for example, while Mr. Juncker hopes to bring the subject up for discussion.