A day earlier, Italy’s finance minister, Vittorio Grilli, told a parliamentary committee that the two treaties were important for the country’s credibility within the European Union. “It is essential that E.U. member states in particular are able to show the clear will to face this crisis with determination and unity of purpose,” he said.

Spain, for its part, does not plan to auction much more debt over the summer, which should at least temporarily ease market pressure on Madrid, if only until September. But by then some fear that the European Central Bank will have to intervene if Spain is to retain its access to financial markets.

“The euro zone has managed to maneuver itself into a dead end,” said Lefteris Farmakis, an interest rate strategist in London for Nomura International. “The clear solution would be for the E.C.B. to intervene, and if it doesn’t I don’t see how Spain can get out of this hole.”

Spain’s borrowing costs had fallen back briefly following a deal among leaders of the 17-nation euro currency bloc at the end of June that would allow aid to go direct to Spain’s struggling financial institutions once a new European regulatory system for banks is in place. The E.C.B also cut its overnight interest rate on bank deposits to zero percent hoping this would encourage the flow of capital to other parts of the euro zone economy.

But Spain’s costs have been inching up recently, partly because of worries about the details of Spain’s bank bailout. That, in turn, has fueled worries that a full rescue for Spain’s government might be needed if its borrowing costs remain at current high levels.

“At the moment it is still a game of chicken, of who is going to blink first, the politicians or the E.C.B?” said Mr. Farmakis. “It is uncertain at what point the E.C.B. steps in. But in the end, one way or another, it will have to happen.”

On Friday the Eurogroup of euro zone finance ministers plans to convene via teleconference, and is expected to agree to the release of a €30 billion portion of the Spanish bank rescue. Separately on Friday, top E.U. officials representing the European Central Bank, the European Commission, and E.U. governments are scheduled to meet to work on details for a centralized bank supervisory body centered around the E.C.B.

Gaia Pianigiani and Elisabetta Povoledo contributed reporting from Rome, Paul Geitner and James Kanter contributed from Brussels, and Raphael Minder from Madrid.