ATLANTA — Nearly a million Americans now have the AIDS virus and the nation’s ability to keep others from becoming infected still lags despite a government pledge four years ago to “break the back” of the AIDS epidemic by 2005.

However, the rate of new cases remains about the same, according to CDC data released Wednesday as part of the federal health agency’s commemoration of World AIDS Day.

“We have a ways to go before we reach the mark of reducing new infections by half in the United States,” said Dr. Ronald Valdiserri, the director of the CDC HIV and AIDS prevention program. He called the country’s HIV infection rate “relatively stable.”

“Clearly we want to continue, and are continuing, to fund programs to reach out to people who are high-risk and are not infected,” he added.

In 2001, the CDC’s campaign focused on outwardly healthy people who did not realize they had HIV — about one-fourth of those infected. Officials then said targeting them was key, because if they knew they were infected, they would be more likely to take steps not to spread the virus.

Such an effort “could possibly break the back of the epidemic in the United States,” the CDC’s Dr. Robert Janssen said then.

But the agency found that just targeting people who didn’t know they had the AIDS virus was not enough. So last year, the CDC shifted gears, focusing on counseling those who knew they had HIV in an attempt to get them not to spread the virus.

“It just doesn’t seem like much is really happening,” said Terje Anderson, executive director of the Washington-based National Association of People Living With AIDS. “There just is a lack of imagination or spark in terms of the kinds of programs they support. I think they are politically afraid.”

“Forty-thousand is an estimate that is averaged over time. The changes can’t be tracked easily from year to year,” said Dr. James Curran, dean of Emory University’s Rollins School of Public Health and the CDC’s former AIDS chief during the 1980s.

“What has concerned many of us in the United States is the lack of attention to the domestic AIDS problem and complacency on behalf of high-risk groups,” Curran said, adding that more counseling, testing and is needed.

The CDC believes up to 950,000 people in the United States are infected with HIV and up to 280,000 of them don’t know it, Valdiserri said.

The rate of HIV diagnoses in the United States increased slightly — by 1 percent — between 2000 and 2003, from 19.5 people per 100,000 population to 19.7 per 100,000 in the 32 states surveyed by the CDC.

A “The reality is, to cut the number of infections, we need to do more — you can’t always do more with less. We desperately need more resources,” Anderson said.