U.S. President Barack Obama, a former smoker himself, has congratulated everyone who has taken part in a national day without using tobacco, while slamming tobacco companies for opposing new labeling requirements.

In a video message, the president said tobacco remains the leading cause of preventable deaths in the United States. He said the country has made progress in reducing the number of Americans who smoke, although 46 million people in the U.S. remain addicted.

The president had strong criticism for tobacco companies, saying they are trying to block graphic, new warning labels because, in his words, “they don't want to be honest about the consequences of using their products.”

His remarks were in observance of the “Great American Smokeout” by the American Cancer Society, a group that works to prevent cancer and tobacco use.

Earlier this year, the U.S. Food and Drug Administration approved nine graphic ads that cigarette companies would have to put on their packages. The ads include images of rotting teeth, diseased lungs, a person smoking through a tracheotomy opening, and the body of a dead smoker.

Cigarette companies have filed legal challenges against the requirement for the new labels, arguing they amount to anti-smoking advocacy.

The president was declared “tobacco free” during his latest physical in October. In his video message, he said quitting smoking is hard, in his words, “Believe me, I know.”