He attributed the increase in this group to poverty, lack of access to healthcare, substance abuse, incarceration and a rise in other sexually transmitted diseases.
"If you are a young, gay black man, the likelihood that you will encounter HIV is staggeringly high, even if your personal behavior is no more risky than people in other communities," said Mark McLaurin, a board member of the Community HIV/AIDS Mobilization Project.
The new data "confirm that AIDS in America is a black disease and has been neglected for far too long," said Phill Wilson, founder and chief executive of the Black AIDS Institute in Los Angeles.
The CDC said that about 1 million to 1.1 million Americans are currently HIV-positive.
But epidemiologist and AIDS expert Philip Alcabes of Hunter College of the City University of New York contends that the new numbers indicate there are about 225,000 more HIV cases in the U.S. than the CDC estimates.
A CDC spokesman rejected his contention, however, saying that the total number of infections is calculated using a different method, and its figure remains accurate.
More than 15,000 Americans die of AIDS each year.
The new data will be formally unveiled today at the International AIDS Conference in Mexico City and published later this week in the Journal of the American Medical Assn.
The CDC has been widely criticized for not releasing the new numbers sooner. Fenton acknowledged that the figures had been available since November, but he said the agency delayed releasing them until they had been accepted for publication.
Dr. Julie Gerberding, director of the CDC, said the paper had been heavily revised during the peer-review process and that she had much more confidence in the findings as a result.
Some critics suspect the results were delayed to avoid embarrassing the Bush administration, which has shrunk the CDC's prevention budget by 19% in current dollars since 2002, according to Rep. Henry A. Waxman (D-Beverly Hills).
"This administration continues to insist on funding ineffective abstinence-only programs that are failing to equip our children with the skills and knowledge necessary to protect themselves," Rep. Barbara Lee (D-Oakland) said.
The new estimates are certain to bring calls for increased spending to combat the epidemic. Even at the old estimate of 40,000 new infections per year, nongovernmental organizations were calling for the United States, which spends $700 million annually on prevention efforts, to boost that figure by at least $300 million.
