A group of U.S. Hispanic leaders has met with Mexico's President Jose Lopez Portillo to ask that he demand greater respect for the human rights of illegal Mexican immigrants in the United States when he visits Washington this week.

After the meeting, spokesmen for the group, representing 11 Chicano organizations, said Lopez Portillo clearly shared their concern and agreed to raise the question once more with President Carter.

The organizations the group represents include La Raza Legal Alliance, the Mexican-American Legal Defense and Education Fund, the League of United Latin American Citizens, the National Association of Farm Worker Organizations and the National Council of La Raza.

The conversation, the spokesmen said, touched on "Mexico's increased bargaining power in the U.S." due to its massive oil reserves, although there was no talk of linking the human rights and energy issues.

Lopez Portillo's meeting with the Chicanos, at a time when he is receiving no other outside visitors relating to his Washington visit, is seen here as a significant new step in the rapprochement between the Mexican government and the Mexican-American movement in the United States.

The White House, according to the Chicano spokesmen, turned down their request to meet with the Mexican president while he is in Washington this week, but Lopez Portillo agreed to see them again a day earlier, in New York, they said.

Last week, the Mexican leader surprised the Chicanos by deciding to formalize the contacts between the two sides by getting up a mixed commission. On the Mexican side, he appointed the ministers of labor and of education, while the Forum of National Hispanic Organizations, which represents 62 Chicano groups, is the umbrella agency in the U.S.

This courtship on both sides of the border is relatively new. Although the previous Mexican administration started the meeting, Mexican politicians for a long time looked on Mexican-Americans with a mixture of suspicion and contempt. The Chicanos often seemed uncomfortably radical to Mexico City. They spoke a different Spanish and obviously had lost touch with their culture.

As the Mexican-American movement has gained strength in the United States and Mexico began to raise its newly powerful voice, the two sides have been regarding each other with new interest.

After calling on Lopez Portillo last year, Chicano leaders here announced they were ready to help Mexico the way American Jews helped Israel and Italian-Americans acted for Italy.

The administration so far has not sought any "help" but officials say it is clearly conscious that the position of the fastest-growning minority group in the United States may affect Mexico in the future.

To avoid the impression that Mexico is meddling in U.S. affairs, the government says it has kept Washington informed of its contacts with Chicano groups.

Through their contracts with Mexico, the Chicano groups apparently also want to strengthen their own image and bargaining position in Washington.

"There is an interesting spinoff effect. To get attention in the U.S., they come here," said Jorge Bustamante, a professor of sociology and longtime student of Mexican migration to the United States. "And in a way it's working. We are aware that American officials are watching these visits more carefully."

The most important common ground for the two sides is their opposition to U.S. attempts to curb the vast illegal Mexican immigration to the United States.

Mexico does not want this vital escape valve closed until its serious economic and social problems have been somewhat alleviated. The Chicano groups say new legislation or policies would intensify racism and police repression, which they say is practiced against all U.S. residents of Mexican or Hispanic descent.

In their meeting with the Mexican president last Thursday, the Chicano lawyers and labor leaders outlined what they described as "escalating police and general human-rights abuse" of illegal Mexican immigrants.

Civil rights attorney Ruben Sandoval, a member of the group, said they showed Lopez Portillo "well-documented cases of police brutality" and warned him of "repressive" bills under discussion, such as a "Texas attempt to make it legal to refuse education to children of undocumented workers, even though they are taxpayers," and also a bill in Congrss to suspend government-funded legal services to undocumented aliens."

Salvador Guerrero, representative of the National Association of Farm Workers Associations, said the Mexican president seemed "very receptive and concerned."

Mexican politicians readily concede that the Chicano groups who defend Mexican citizens in the United States are basically performing a duty of the Mexican government. Therefore, they say, the Mexican administration has no choice but to raise the subject with its American counterpart.

A more skeptical view here is that, given the authoritarian system of Mexico, the president is not likely to press very hard for the rights of Mexicans in the United States.

"The next thing you know is that the Americans raise the (subject of) human-rights violations within Mexico, and that's not something the government wants," said a lawyer who opposes the current Mexican administration.