CNN on Thursday re-tracted its story that the U.S. military used deadly nerve gas during a Vietnam-era mission in Laos to kill American defectors.

CNN said its internal investigation concluded that its report, disputed by "hundreds" of veterans and military officials, could not be supported.Tom Johnson, chairman of the CNN News Group, issued a statement apologizing to viewers and to U.S. military personnel.

CNN had hired attorney Floyd Abrams late last week to conduct an independent investigation into the charges, and made its statement Thursday based on his report.

Johnson said reporters, producers and executives at CNN bear responsibility for the mistake, but in a report aired shortly after noon on CNN did not say what action will be taken against them.

The story proved a major embarrassment to CNN/USA President Richard Kaplan. Launch-ing a series of newsmagazines called "News-Stand" was his top programming initiative, and he used the nerve gas story to attract attention to the series' premiere.

Almost immediately after it was aired, military experts began disputing the contention that the lethal nerve gas sarin was used on a Laotian village in 1970, as part of a secret mission to kill American defectors.

Defense Secretary William Cohen ordered an investigation into the charges, but said there was no evidence that the gas was ever used.

CNN military analyst Perry Smith, a retired major general who served in Vietnam, called the account "sleazy journalism" and resigned in protest. He said he was not consulted on the story before it aired.