US President Barack Obama has not smoked a cigarette in almost a year, First Lady Michelle Obama has said.
Mrs Obama said she was very proud of her husband, who had smoked for years and has repeatedly spoken of his struggle to quit tobacco.
In December, White House spokesman Robert Gibbs said he had not seen the president smoke in nine months.
After a 2010 medical examination, Mr Obama was told by Dr Jeffrey Kuhlman he should continue trying to quit smoking.
On Tuesday, Mrs Obama explained that her husband wanted to be able truthfully to tell his daughters Malia, 12, and Sasha, nine, that he did not smoke, should they ask.
'Off the wagon'
Mr Obama, who began smoking as a teenager, had promised his wife he would kick the habit if she would allow him to run for president.
"Look, I've said before that as a former smoker I constantly struggle with it," Mr Obama told reporters in 2009.
"Have I fallen off the wagon sometimes? Yes. Am I a daily smoker, a constant smoker? No. I don't do it in front of my kids. I don't do it in front of my family. And, you know, I would say that I am 95% cured."
Other heads of state have struggled with nicotine addiction.
In March, then-Brazilian President Luiz Inacio Lula da Silva said he had stopped smoking after 50 years using only will power. Mr Obama has acknowledged using nicotine gum.
Lula declined to press Mr Obama to quit, saying: "On these sort of things, you don't give advice. Everyone can do what they want if they're of age. Everyone knows that it's not good for your health."
And one of Mr Obama's top Republican adversaries, House Speaker John Boehner, is an avowed cigarette smoker.
Some Washington media figures have suggested the two quit together as a gesture of good will and to be better role models for American youth.
Mr Boehner told an interviewer last autumn that he appreciated the suggestion.