If the tests of the 91 banks are credible, they would separate the minority of sick banks from the healthy majority. Banks would be more willing to lend to each other. And the solid banks could sell bonds to raise money that they could in turn lend to businesses and consumers, promoting economic growth.

“Without a solid financial sector, I don’t think we will have any kind of sustainable recovery,” said Diego Iscaro, senior economist in London at IHS Global Insight, a market research firm. “If we don’t have full transparency, it’s going to be an opportunity missed.”

Analysts say that some banks should fail the stress tests, though they disagree on how many. In a study issued Tuesday, the Japanese bank Nomura said 16 European banks were likely to need more capital in order to be adequately insulated against economic and market shocks. The weaker institutions included several Greek and Italian banks, as well as Deutsche Postbank.

A Nomura analyst, Jon Peace, cautioned that the banks’ criteria might not be the same as those being used by regulators and so they did not predict the results of the official stress tests.

A study by Credit Suisse found that all but two Greek banks would have enough capital. Credit Suisse and Nomura looked only at publicly traded banks in detail, not at public-sector institutions like the German landesbanks or Spain’s savings banks, known as cajas — both of which are considered vulnerable by many analysts. Europe’s public-sector banks could require €90 billion in additional capital, Credit Suisse estimated.

The cajas spearheaded lending to the Spanish construction sector, and suffered when it collapsed. In many cases, the cajas have not been able to respond effectively, because they have been held hostage to the interests of the politicians who control them.

Many of the landesbanks, which have close links to state governments, invested in derivatives tied to the U.S. real estate market or other toxic assets.