A group of black businessmen yesterday attacked a proposal to increase the number of groups eligible to participate in Washington's minority contracting program, saying that those other than American blacks should be required to prove they suffered discrimination.

"European Hispanics and people from Asia should have a burden of proving they were discriminated against," said Roy Littlejohn, president of Save-More Foods Inc. and a leader of the business group, the Coalition to Protect Black Businesses.

Littlejohn said the program, under which 25 percent of city business is set aside for minorities, should be limited to those who have been "systematically discriminated against by institutions in the United States."

The group called a press conference in the District Building yesterday to attack an amendment that would expand the program to include Asian Americans, Pacific Islanders and Hispanics of European origin. Two weeks ago, the D.C. City Council approved the amendment and is scheduled to take a final vote on it today.

City Council member John A. Wilson (D-Ward 2), a sponsor of the amendment, said yesterday that now there may not be enough votes on the council for final passage of the amendment. He said votes for it have been slipping away since the Sept. 14 primary and that the amendment is in "serious difficulty."

The measure was given tentative approval Sept. 21 on an 8-to-3 vote with two council members absent.

The amendment also seeks to raise the 25 percent requirement to 35 percent, a figure that Littlejohn and his group said should be 50 percent.

At yesterday's news conference, Carthur L.M. Drake of DAC Corp., a food service catering corporation that, like Littlejohn's, has contracts with the city, said the language of the amendment would qualify members of more than 67 additional minorities to participate in the program.

He said these would include "minorities from Iran, China, Israel, Thailand, Japan, the Soviet Union and others who have origins in the continent of Asia."

Wilson did not dispute the number of countries of origin that could be included, but he said the amendment "would allow only American citizens who are considered minorities by the federal government in this country the opportunity to be involved in this program.

Drake said that if the amendment passes today, the group will redouble its lobbying efforts to kill it.