FRANKFURT — If the past is any guide, European Union leaders will leave their summit meeting this week waving promises to weave the euro zone more tightly together. They are likely to back a plan to finance infrastructure projects in stricken countries.


But unless the usual expressions of resolve are bolstered by concrete action or at least a binding timetable, financial markets are likely to continue to penalize Spain and other troubled countries by pushing up their borrowing costs to levels that will eventually prove unaffordable.


“We know by experience that recent summits have generated expectations that were not met by decisions,” Joaquín Almunia, vice president of the European Commission, said in Frankfurt last week. “We at the European Commission hope that this time will be different.”


The ideal outcome from the meeting in Brussels on Thursday and Friday, as a rising chorus of central bankers and foreign leaders has made clear, is deliberate movement toward a euro zone in which countries would backstop one another’s banks and bonds, while at the same time policing one another’s spending.


On Sunday, the Bank for International Settlements, a clearinghouse for central banks whose board includes the Federal Reserve chairman, Ben S. Bernanke, was the latest to urge euro zone leaders to establish a banking union, including stronger measures to guarantee deposits and prevent bank runs. The International Monetary Fund and the European Central Bank have made similar pleas.


European leaders are not blind to the dangers confronting the euro zone.


Wolfgang Schäuble, the German finance minister who is known as an advocate of a stronger European central government, said in an interview published Sunday that Germany may need to hold a referendum on a new constitution within several years, to make it easier for the country to cede budgetary authority. “In some important political areas we need to transfer more jurisdiction to Brussels, so that not every decision can be blocked by any member state,” Mr. Schäuble told the magazine Der Spiegel.


In another indication of the pressure that leaders feel, Chancellor Angela Merkel of Germany is scheduled to meet President François Hollande of France in Paris on the eve of the summit meeting. The two leaders are expected to try to build at least a working relationship, as Ms. Merkel had with Mr. Hollande’s predecessor, Nicolas Sarkozy.


The reason European leaders are not expected to do anything drastic is that they have not been able to find a way to break the fundamental deadlock between northern countries, led by Germany, and southern countries like Spain and Italy and their ally, France.


Leaders like Mario Monti, the prime minister of Italy, want to co-opt Germany’s stellar credit rating to lower their own borrowing costs. Ms. Merkel, backed by Germany’s central bank and most of the German public, refuses to do that without also having much more say about how the Italians and others spend the money.


A meeting of leaders of the four largest countries in Rome on Friday suggested what might be expected from the full meeting this week. The leaders of Germany, France, Italy and Spain agreed to a 130 billion euro ($163 billion) growth pact, which mostly redirects existing funds. It would also create so-called project bonds, with the euro zone providing credit to private companies for infrastructure projects and job creation.


While helpful, the plan, which is expected to be formalized at the meeting, does not address the underlying weaknesses in the architecture of the euro zone.


“The outcome of the summit,” Commerzbank economists said in a note to clients, “will only be to produce an economic stimulus program which will have at best a limited effect.”


And so the euro zone continues to stumble toward what even normally restrained observers fear could be disaster. Spain’s borrowing costs continued their steep climb last week and, without decisive action on a grand vision for the region, are bound to be punished in the week ahead.


The days leading up to the summit meeting are likely to be tense, adding to the feeling that European leaders are running out of time.


“The very survival of the euro is under threat,” Athanasios Orphanides, until the end of May a member of the governing council of the European Central Bank, said in Frankfurt last week.


Greece’s new government must in the days ahead satisfy voter expectations that it will be able to renegotiate the austerity imposed by international lenders.


Spain is expected to begin bargaining with European officials about the terms of a bailout of its banks, who need as much as 62 billion euros in fresh capital, according to audit reports last week.


Spain illustrates the dysfunctional relationship between banks and governments and why a banking union is seen as urgently needed. After European leaders committed 100 billion euros, or $125 billion, to recapitalize Spanish banks this month, market relief lasted only a few hours. Investors realized that the Spanish government, whose size is dwarfed by the country’s banks, was still liable for the cost of the bailout. The additional burden made Spain look even less creditworthy than before.


A banking union would go a long way toward insulating countries from the woes of their banks, and vice versa, proponents say.