The HIV infection rate has doubled among blacks in the United States over a decade while holding steady among whites - stark evidence of a widening racial gap in the epidemic, government scientists said Friday.

Other troubling statistics indicate that almost half of all infected people in the United States who should be receiving HIV drugs are not getting them.

The findings were released in Boston at the 12th Annual Retrovirus Conference, the world’s chief scientific gathering on the disease.

“It’s incredibly disappointing,’’ said Terje Anderson, director of the National Association of People With AIDS. “We just have a burgeoning epidemic in the African American community that is not being dealt with effectively.’‘

Researchers and AIDS prevention advocates attributed the high rate among blacks to such factors as drug addiction, poverty and poor access to health care.

The HIV rates were derived from the widely used National Health and Nutrition Examinations Surveys, which analyze a representative sample of U.S. households and contain the most complete HIV data in the country. Researchers at the Centers for Disease Control and Prevention compared 1988-1994 data with figures from 1999-2002.

The surveys look only at young and middle-aged adults who live in households, excluding such groups as soldiers, prisoners and homeless. Thus, health officials believe the numbers probably underestimate true HIV rates in this country.

Still, they show a striking rise in the prevalence of the AIDS virus from 1 percent to 2 percent of blacks. White rates held steady at 0.2 percent. Largely because of the increase among blacks, the overall U.S. rate rose slightly from 0.3 percent to 0.4 percent.

Smaller studies had shown rising infection rates among blacks in recent years, but this study takes a longer and more complete look at changes in the general population.

“I think it’s very concerning,’’ said Dr. Susan Buchbinder, who leads HIV research for the city of San Francisco. “I think what we need to look at is how we can reduce those rates and get more people into treatment.’’