WASHINGTON, May 17: A tearful President Bill Clinton formally apologized on Friday for the government's infamous 40-year experiment, in which doctors deliberately withheld treatment from syphilitic black men.

At a White House ceremony, the President told five of the experiment's eight survivors and the families of nearly 400 infected participants that there were no excuses for the government's behaviour.

Between 1932 and 1972, the men, mostly poor and illiterate black male farm workers, served as human guinea pigs for US health officials curious about how the disease progressed when untreated.

The so-called "Tuskegee Experiment" named after the Alabama town where it occurred came to an end only after it was uncovered by the press.

"I apologize and I am sorry that this apology has been so long in coming," Clinton said at the ceremony, which included survivors ranging in age from 91 to 100. "I am sorry that your federal government orchestrated a study so clearly racist."

The White House, which is making racial healing a top priority of Clinton's second term, billed the apology as a symbolic atonement for the experiment itself and for officially sanctioned wrongs inflicted by authorities on blacks and other US racial minorities.

In the 1970s, the government was forced to pay 10 million dollars as damages to the survivors and families of participants who had died.

The test subjects were lured into the programme with promises of free food, free transportation and assurances that they would get free treatment for blood problems. Of the 600 people who signed up, 399 had syphilis. The infected men were told only that they had "bad blood" and were given placebos even after penicillin became available in the 1940s. During the course of the experiment, 28 of the test subjects died of syphilis and another 100 died of complications related to the disease. Forty women, spouses of the subjects, also contracted the infection.