For years, interest groups have fought off efforts at greater regulation
The US Senate has backed a bill giving the government far-reaching new powers to try to curb smoking among Americans.
If approved by the House of Representatives, the bill will permit nicotine levels in cigarettes to be limited and advertising curtailed.
Commentators hailed the vote as a major victory against vested tobacco interests which for years have sought to frustrate regulatory efforts.
About 20% of Americans smoke, and the habit kills some 440,000 every year.
President Barack Obama hailed the passage of the bill, saying it would "make history by giving the scientists and medical experts at the FDA [Food and Drug Administration] the power to take sensible steps that will reduce tobacco's harmful effects".
It was also applauded by anti-smoking and health campaigners.
Focus on children
By a margin of 79 to 17, the Senate passed the bill giving the FDA powers to regulate the content and marketing of tobacco products.
- Limiting nicotine levels - though not banning nicotine or cigarettes entirely
- Attempting to limit the appeal of smoking among young people, by limiting the use of flavours, restricting advertising in publications targeting young people, and toughening rules on sales to young people
- Requiring tobacco companies to get FDA approval for new products
- Barring terms such as "light" or "mild" in tobacco packaging which imply a smaller risk to health
- Requiring tough new warning labels on tobacco products.
The bill is particularly focussed at curbing the take-up of smoking among children, and was hailed as such by a leading supporter, Democratic Senator Dick Durbin.
"Every day that we don't act, 3,500 American kids - children - will light up for the first time. That is enough to fill 70 school buses," he said.
The House of Representatives adopted a similar bill in April, and Speaker Nancy Pelosi said she believed it might be possible for the House to accept the bill in its entirety when it votes on Friday.
If so, it would go straight to President Obama to be signed into law.
Repeated efforts by supporters of greater regulation of the tobacco industry have been fiercely resisted for years by the industry and lawmakers from tobacco-producing states.
This time, the country's biggest tobacco firm, Philip Morris, supported the bill - though rivals suggested that was because restrictions on new products would protect the company's market share.
Observers said the bill was one of the most momentous milestones in the history of smoking since the 1964 surgeon general's report highlighted the hazards it posed to health.
"This legislation represents the strongest action Congress has ever taken to reduce tobacco use, the leading preventable cause of death in the United States," said Matthew Myers, president of Campaign for Tobacco-free Kids.
"At any given moment, millions are struggling with their habit or worrying about loved ones who smoke," said President Obama, who has spoken of his own effort to quit and admits he occasionally still smokes.
"My administration is committed to protecting our children and reforming our health care system - and moving forward with common-sense tobacco control measures is an integral part of that process. I look forward to signing this bill into law."