WASHINGTON (AP) _ Minority-owned companies grew four times as fast as U.S. businesses overall in the 1990s, but racial disparities still exist when it comes to generating revenue, the Commerce Department said Thursday.

Minorities owned 2.8 million companies, or 15 percent of American businesses, in 1997, up from 2.1 million, or 12 percent of U.S. companies in 1992, according to data from a survey conducted by the department's Census Bureau.

The 30 percent growth rate in minority-owned companies outpaced the 7 percent increase for all U.S. businesses during the same time period.

But more grass-roots efforts are needed to stimulate start-up business and strengthen existing companies to ensure that minority representation in the business world matches the nation's demographic makeup, said Ronald Langston, director of the department's Minority Business Development Agency.

In 1997, minorities made up 27 percent of the country's population.

And, minority-owned businesses fell short of the national average when it came to generating revenue.

For instance, all U.S. manufacturers, regardless of the race and ethnicity of the owner, generated an average of $5.8 million in receipts in 1997. But manufacturing companies owned by a minority generated an average of $991,000 in receipts.

``We have made great achievements, but today's data indicate that there are more challenging opportunities ahead,'' Langston said.

Specifically, he said the agency was developing programs to increase access to capital for prospective business owners, and increase minority-owned manufacturers.

Comparisons between 1992 and 1997 excluded certain types of businesses, called ``C'' corporations. The 1997 survey was the first to include such corporations.