Mexican President Enrique Peña Nieto announced plans Wednesday to boost access to credit for small businesses, promising changes in banking aimed at bringing down the usurious lending rates that have long been viewed as an obstacle to growth and an impetus for illegal immigration to the United States.

For generations, would-be Mexican entrepreneurs have gone north in search of the seed money needed to start a business back home, while others resort to informal lending networks whose annual interest rates can top 50 percent.

Flanked by leaders of other major Mexican political parties pledging their support, Peña Nieto said the measures were essential to create jobs and to provide “a motor” for the economy, adding that his administration will work with lenders to loosen credit through incentives and legal guarantees, not “by decree.”

“The goal is for banks to loan more, and loan more cheaply,” said Peña Nieto, who took office in December, “because access to credit can change a person’s life, giving them access to durable consumer goods, their own property and a way out of the informal economy.”

Economists estimate that one-quarter to one-half of Mexicans work in the “informal” sector, the off-the-books bazaar of churro vendors, fruit stands and other forms of micro-commerce that rarely offers more than a subsistence living. Providing those entrepreneurs with affordable banking services and credit is viewed as a key step toward building a broader Mexican middle class.

The changes in lending are a keystone of Peña Nieto’s legislative agenda, which also contemplates an overhaul of Mexico’s energy, telecommunications and education sectors. The new measures would foster more competition in the banking sector and lift some of the tight controls placed on lending after the 1995 peso crisis, said Luis Videgaray, Mexico’s treasury secretary and one of the president’s closest advisers.

Lending as a percentage of gross domestic product is about 16 percent in Mexico, he said, while the average in Latin America is closer to 50 percent.

Mexico’s finances are on solid footing, Videgaray said, and banking services dedicated to development have become “too conservative.”

“The purpose of development banking should be to finance innovation, the creation of patents, infrastructure . . . it should be a bank that promotes equality between men and women,” he said, also highlighting plans to increase small-business lending for women in particular.