Twice as many Americans may be infected with the AIDS virus as the government estimates, and the level of infection among heterosexuals appears grossly understated, a public policy group said Friday.

A study conducted by the Hudson Institute concluded "a best guess at the range of total infections as of year-end 1987 (was) from 1.9 million to 3 million persons, with the likeliest range between 2.2 million and 2.6 million people."A spokeswoman for Centers for Disease Control in Atlanta said the federal agency estimated that at the end of last year, 900,000 to 1.4 million Americans were infected with the Human Immunodeficiency Virus, which causes acquired immune deficiency syndrome. She refused to comment Thursday on the Hudson estimates.

Dr. George Keyworth, director of research for Hudson, called the findings "a sober warning to AIDS skeptics.

"Even though no one knows for certain how many people in the United States are infected, this report pointedly suggests that we may be gravely underestimating the extent of the epidemic. The disease may be spreading much faster than has been generally believed," Keyworth said in a prepared statement.

Hudson researchers Kevin Hopkins and William Johnston said they were concerned with calculations that showed a surprising amount of HIV infection in heterosexuals who did not use intravenous drugs.

Gay men and intravenous drug users have been the groups considered at highest risk of being infected with the AIDS virus. HIV is spread through sexual intercourse and blood-to-blood contact, such as by sharing contaminated needles or through inadequately screened blood transfusions.