Washington ? Lamenting his first teenage cigarette, President Barack Obama ruefully admitted on Monday that he’s spent his adult life fighting the habit. Then he signed the nation’s toughest anti-smoking law, aiming to keep thousands of other teens from getting hooked.

Obama praised the historic legislation, which gives the Food and Drug Administration unprecedented authority to regulate what goes into tobacco products, to make public the ingredients and to prohibit marketing campaigns geared toward children.

But he didn’t say how his own struggle was coming since he moved into the White House. And aides were no more forthcoming.

As senator, candidate and now president, Obama has veered between frank and cagey about his personal battle with smoking.

He promised his wife, Michelle, more than two years ago that he would quit if she let him seek the White House.

He has often acknowledged since that he has “fallen off the wagon.” But he hardly ever provides specifics. And though White House aides pack nicotine gum in their jackets to help him resist, they also refuse to give a clear answer to the question of whether the president still sneaks a smoke now and again.

During Obama’s two-year White House bid, he was known to occasionally bum a cigarette from a staff member — while also making sure to emphasize his efforts to stop for good and his progress from his onetime five-smoke-a-day average.

During Monday’s bill signing, Obama focused on how the new law would help keep future generations of kids away from the dangerous habit. The president mentioned his own experience very briefly — just 30 words.

Almost 90 percent of people who smoke began at 18 or younger, he said.

“I know. I was one of these teenagers,” he said. “And so I know how difficult it can be to break this habit when it’s been with you for a long time.”

And then he went back to the merits of the bill and the shortcomings of the tobacco industry, which he accused of targeting young people. One key provision in the new law bans candy-flavored cigarettes and the use of other flavored smokes that might appeal to teenagers. Ads aimed at young people also are banned.

Aides refused to elaborate on his own situation.

White House press secretary Robert Gibbs said he hadn’t asked Obama about his smoking and made plain that he didn’t plan to. The presidential spokesman stuck to vague language that left the impression Obama still occasionally falls off the wagon, but he did not say so directly.