In an interview with The Associated Press, Dr. Andrew von Eschenbach said that if the FDA reduced nicotine levels in cigarettes, people would tailor their smoking habits to maintain current levels of the addictive drug.
"We could find ourselves in the conundrum of having made a decision about nicotine only to have made the public health radically worse. And that is not the position FDA is in; we approve products that enhance health, not destroy it," said von Eschenbach, a cancer surgeon.
A bipartisan group of lawmakers introduced legislation last month that would give the FDA the authority to regulate tobacco, in part by reducing its nicotine content.
Smoking kills more than 400,000 Americans a year.
Von Eschenbach said repeatedly that the issue of regulating tobacco is a complex one.
"What I don't want to see happen is that we are in a position where we are determining that a cigarette is safe," von Eschenbach said.
In 1996, the FDA moved to regulate tobacco. The Supreme Court ruled in 2000 that Congress had not authorized the agency to do so.