FRANKFURT — The European Central Bank took steps on Thursday to address a credit squeeze in Southern Europe, making it easier for banks to bundle loans into securities that they could resell to investors and raise money for additional loans.

It is too soon to predict how much effect the central bank’s action will have on the euro zone economy. The change will take effect in October. But in theory, the measures should free up credit for businesses that want to invest in new equipment or larger premises, or for consumers who would buy new cars or homes.

Lack of credit in countries like Italy and Spain has been a big reason those countries are stuck in recession. Lending to businesses and consumers in the euro zone as a whole has been in steady decline, falling at an annual rate of 1.1 percent in May, according to the central bank’s data.

The European Central Bank plans to revise its rules to make it easier for banks to use bundles of loans, known as asset-backed securities, as collateral for low-interest loans from the central bank. Banks will be able to use the securities to obtain loans from the central bank at its benchmark interest rate, currently 0.5 percent.

The change should help encourage a livelier market for the securities. Banks will be able to profit from the difference in the interest rate they collect from borrowers or investors, and what they pay the central bank.

Mario Draghi, the central bank president, had said in recent months that the bank was looking for ways to encourage lending to small business. But the bank seemed to be struggling to find a way to do so.

Marie Diron, an economist who advises the consulting firm Ernst & Young, said that the bank might have felt pressure to act because of turmoil in the euro zone bond market and political tensions in Italy, Spain and Portugal.

“This action is very small, though,” Ms. Diron said. She quoted estimates that the move would increase the total assets that could be used as collateral by about 20 billon euros out of a pool of assets worth about 15 trillion euros. That, she said, “is hardly going to be a game changer.”

Throughout Europe, many banks are struggling with large numbers of bad loans, which weigh on profits and make it difficult for them to issue new loans. Because their financial health is suspect, many banks also have trouble raising money from investors that they can then lend to customers.

Asset-backed securities help solve this problem. If a bank bundles loans and sells them to investors, it does not need to worry about the loans anymore and can use the money to make new loans. Credit is crucial to economic growth, allowing restaurants to renovate and expand, taxi drivers to buy new vehicles and factories to buy new machinery.

Asset-backed securities acquired something of a bad name during the financial crisis, because banks used them to package large numbers of questionable loans in a way that concealed much of the risk from investors. When investors lost faith in the securities around 2008, they declined sharply in value. Some asset-backed securities had been sliced up and repackaged so often that investors were unable to figure out what the underlying assets were worth.

The central bank appears to be acutely aware of this problem. It will accept asset-backed securities only when information about the underlying loans is available to investors in an electronic database. And it will not accept securities that have been repackaged several times.

Because the bank tightened collateral requirements for some other kinds of securities, the net effect on lending will probably be small initially. Over the long run, though, the impact could be more significant if it helps revive the market for asset-backed securities.

The European Central Bank also said it was moving forward on a plan that would extend collateral privileges to small-business loans guaranteed by the European Commission or the European Investment Bank, a publicly owned development bank. But that change is also likely to involve relatively modest sums of money.

To some extent, the lack of lending in countries like Portugal and Greece reflects the dismal economic situation there. Business owners may be too pessimistic about the economy to want to invest in new equipment or larger premises. That is a problem the central bank cannot solve.