The powerful Food and Drug Administration (FDA) made the claim in a letter to Congress, which also urged that cigarettes should be treated as potentially hazardous drugs whose sale should be subject to government controls.
The letter said that in the course of the manufacturing process, nicotine extract is sprayed on to sheets of tobacco fibre before they are shredded for use in cigarettes.
David Kessler, the head of the FDA, said that companies were adding nicotine in this way 'to achieve drug effects in some smokers'.
The letter, which was signed by Mr Kessler, represents an extraordinary shift in official attitudes in the US and a big step in the direction of regulation - possibly even prohibition in the long run - of most tobacco sales.
Mr Kessler acknowledges that subjecting tobacco to government controls 'could mean, ultimately, removal from the market of tobacco products' that contain high levels of nicotine. The implication is that only nicotine-free cigarettes could still be freely sold.
Congress immediately agreed to hold hearings on the FDA proposal, but members are certain to come under fierce pressure from the tobacco lobby to resist legislation.