Mayor Marion Barry, who two weeks ago signed legislation reinstating all Hispanics and Asians as eligible groups for the city's $140 million-a-year minority contracting program, has asked the City Council to amend the law by limiting the number of Hispanics and Asians who qualify.

Barry's proposal, now pending before the council, does not specify which Hispanics or Asians would be ineligible for the program. In a letter accompanying the measure Barry said he objects to the current bill because it identifies minorities by ethnic group as well as by "geographic distribution."

"Such a broad definition will create extraordinary problems in our attempts to administer the legislation," Barry wrote in the letter to council Chairman Arrington Dixon. "For instance, there are by definition more than 60 Asian countries. It is not my belief that council intended to grant preference to immigrants from all of those countries."

Courtland V. Cox, a special assistant to Barry and former director of the city's Minority Business Opportunity Commission, said he had looked at judicial and legislative history of government programs to remedy discrimination and found a need for some proof of discrimination against groups receiving preferential treatment.

"There has to be a test before the administration can come to any conclusion," Cox said. "The test would be whether in fact a group, if that group stood alone, would justify the need for this bill and preferential treatment."

The change proposed by Barry in the language of the bill would alter the operating definition of minority. As now written, the bill makes all minority groups listed including black Americans, native Americans, Asian Americans, Pacific islander Americans and Hispanic Americans eligible for the program.

Barry's change would limit eligibility to "those . . . " who because they are members of the foregoing groups, have been economically and socially disadvantaged because of historical discrimination practiced against these groups by institutions within the United States of America."

The language of the proposed change appears to place the burden on all minorities to prove that they have been discriminated against.

"One way to read this bill," said council member David Clarke (D-Ward 1), who cosponsored the bill to put Hispanics and Asians back in the program, "is that those black Americans who are rich . . . couldn't qualify . . . . Barry supported a lot of people who wanted this bill changed and lot of people who did not. That's where his headache is."

Barry, in his letter to the council, does not say what test should be used to determine if a group or member of a group qualifies for the program.

"No one knows at this point what he wants to use," said council member John A. Wilson (D-Ward 2), another cosponsor of the recently passed legislation. "He's trying to limit the number of people participating in the program but he hasn't established guidelines that leave anybody out, as far as I can see."

The Minority Contracting Act has been a controversial measure because black businessmen, particularly the Coalition to Protect Black Businessmen, has argued that the value of the program as an aid to minorities has been diluted by including minority groups such as Hispanics from Europe and Asians.

The businessmen contend that members of those minority groups do not face the same degree of discrimination that blacks, for instance, face in trying to do business.

The initial law was passed in 1976, but in 1980, the council removed those groups from the law. In September, the Clarke-Wilson bill reinstating those groups was given final approval by the council.

Malcolm Beech, president of the D.C. Chamber of Commerce and a member of the black businessmen's coaltion, said yesterday he is not pleased by the mayor's proposal.

"We are asking that the bill remain the same as it was," he said. "What Mayor Barry has proposed is something in between what we want and the bill he signed a few days ago. It's not what we want, but we'll work with it. . . . Our fear is that people coming over here can wipe out black business in the city."

Alan Cheung, a spokesman for the Organization of Chinese Americans, said he was surprised that the mayor is trying to amend the bill he recently signed.

Cheung sid Barry had promised his group before the September primary that he would sign the legislation including Asians and Hispanics in the minority contracting law if it came to him from the council.

"My immediate reaction is to be a little disturbed," said Cheung. "This is harassment and discrimination based on economic resources. Asians hold less than 5 percent of the contracts, but we are fighting it on the basis of principal and equal opportunity. We deserve to be included."

Eduardo Perdomo, head of Perdomo & Associates, a contracting firm, and former president of the Hispanic American Construction Enterprises, said he could not understand why the mayor would want to reopen the controversy.

"To say that only some Hispanics or some Asians could be included that would be a kind of discrimiation," he said. "I don't understand how he could do it. Would Puerto Ricans and Cubans be included but not Argentinians . . . I don't know what he's doing but it's dangerous. This is very disturbing."