WASHINGTON — Marriott International Inc., the nation's largest hotel chain, said yesterday it will ban smoking in all of its 400,000 hotel rooms in the United States and Canada, casting the decision as less about public health and more about taking care of the bottom line.

Two decades ago, about half of the company's rooms were set aside for smokers, but demand has steadily dropped, with only 5 percent of customers now requesting smoking rooms. At the same time, complaints about cigarette odor have increased, and company officials have struggled for ways to solve them.

The move by Marriott, which will enforce its ban by charging violators $200 to $300, follows that of the Westin Hotels & Resorts chain, which late last year announced it was making all 77 of its properties smoke-free. Since then, business has grown stronger, said Sue Brush, a senior vice president with Westin, which is owned by Starwood Hotels and Resorts Worldwide Inc.

Marriott has six hotel properties in Hawai'i.

David Webb of Huntsville, Texas, who was staying at a Ritz-Carlton in Washington D.C., was smoking yesterday. He said he requests nonsmoking rooms because he "cannot stand the smell of old smoke in rooms." He smokes outside and said a smoke-free environment is an incentive to stay at a Marriott property.

Airlines only prohibited smoking on their flights after the federal government passed a law requiring such bans in the 1990s. Restaurants and bars are increasingly becoming smoke-free zones, now that more than 2,200 municipalities have smoking restrictions. Marriott executives said there was no government involvement in their decision to end smoking in the rooms of their 2,300 hotels.

The Bethesda, Md.-based company, which had been reserving 10 percent of its rooms for smokers, said the decision was most closely tied to guest satisfaction.

"Complaints about smoking is one of the biggest complaints we have," said Steve Lampa, the company's senior vice president of room operations and quality assurance. "Clearly there will be some guests who smoke that won't agree with this decision and may decide to move elsewhere. We don't think there will be a negative financial impact."

Marriott executives considered Westin's positive experience with its ban when making their decision, the company said. Executives also acknowledged they were influenced by the reported dangers of secondhand smoke, including a recent surgeon general's report on the subject.

Several industry observers think there is a good chance other major hotel chains will follow Marriott with their own smoking bans. About 21 percent of the U.S. population smokes.

"This tips the hotel industry so now virtually every hotel will have to go nonsmoking," said Edward Watkins, editor of Lodging Hospitality, a leading trade publication. "Marriott is the leader of the pack. Once they do it, every company will have to do that. They just have so many hotels. It's a matter of competitive pressure."

Public health and anti-smoking advocates cheered the move as a key victory in their attempts to eliminate exposure to secondhand smoke.

Frances Stillman, co-director of the Institute for Global Tobacco Control at Johns Hopkins University, said Marriott's decision was particularly important for public health advocates' efforts to shake off arguments by the tobacco industry that smoking bans are bad for business.

"This decision is proving that it doesn't hurt business to ban smoking," said Stillman, who is on the faculty of the university's Bloomberg School of Public Health. "Finally, the economic argument and the public health argument are coming together. Companies are realizing that public health is good for business."

Smoking-rights advocates were not pleased.

"We believe it is discrimination, and we are not going to recommend to our members that they stay at a Marriott-branded hotel," said Thomas Briant, executive director of the National Association of Tobacco Outlets, which represents tobacco manufacturers, distributors and retail outlets.

Several dozen hotels, mostly boutiques, followed Westin's move last year.