LOUISVILLE, Ky. - Tobacco advocates used to being on the defensive in their own country are fuming over a Canadian proposal they say could essentially ban some American leaf often used in cigarettes sold north of the border.

The measure, which was passed earlier this week by the House of Commons, would outlaw selling tobacco embellished with fruit and candy flavors, which health officials say entice youngsters to smoke.

Supporters of the cash crop worry American burley -- a variety commonly blended with other types of tobacco and laced with flavors to smooth its harsh taste -- will be snarled in the ban.

They also fear the measure, which is now awaiting Senate approval, encourage other countries to enact similar restrictions.

The bill was passed by Canada's House of Commons this week and went to the Senate. Tobacco officials and their Congressmen hard to keep the bill from passing, arguing the livelihood of farmers and manufacturers is in jeopardy.

Roger Quarles, president of the Burley Tobacco Growers Cooperative in Lexington, Ky., said the flavorings added to burley are undetectable to consumers.

"They've dumped our American-blend cigarettes in the same class as something that tastes like candy," said Quarles, who grows about 45,000 kilograms of burley each year, and who recently planted his 38th tobacco crop in central Kentucky.

A spokeswoman for Canada's health department, Christelle Legault, said the bill has no restrictions on burley, but instead is aimed at making cigarettes less accessible and appealing to youths.

Legault cited statistics from a 2007 study, the most recent available, showing 25 per cent of Canadian youths aged 15 to 17 reported having tried a little cigar, also known as a cigarillo. And 42 per cent of youths aged 18 to 19 had tried the small cigars, which are often flavored.

The bill has drawn criticism from Canadian tobacco company Rothmans, Benson & Hedges Inc., an affiliate of Philip Morris International (NYSE:PM) RBH imports burley to make such American-blend cigarettes as Rooftop, Carreras, Gitanes and Gauloises, which represent a small but important part of its production. The company said in a statement that flavorings added to burley "have nothing to do with enticing minors to smoke."

RBH president John Barnett said the bill could seriously curtail production at the company's factory in Quebec, which employs 300 people.

The lobby group Physicians for a Smoke-Free Canada responded to the company's complaints Friday by urging it to "butt out" of Canadian health-care policy.

"Philip Morris has a long history of threatening trade action against health measures around the world," executive director Cynthia Callard said in a statement.

The proposed law, she said, would not ban the import of U.S. cigarettes, result in any lost jobs north of the border or make Canada vulnerable to trade challenges, she added.

Callard accused the company of trying to play for time. "Philip Morris is throwing up sand, hoping for delay."

But the fear in the U.S. appears less concerned with the Canadian market than it does with the example the legislation could set.

About 80 per cent of U.S. burley is exported, and the prospect of losing a vast market has inflamed farm groups and their political allies from tobacco-producing states.

"If other countries follow Canada's lead, the market for American-style tobacco products will be nonexistent outside the U.S.," said Wayne Pryor, president of the Virginia Farm Bureau Federation.

In a recent letter to Canadian officials protesting the measure, Kentucky Farm Bureau President Mark Haney called it an "overreaching attempt" that would "destroy a legal market in Canada" and kill U.S. agricultural jobs.

U.S. burley production has plummeted since the demise of a government quota system earlier in the decade and as smoking bans gained a solid foothold. Yet the leaf remains an important cash crop for about 8,100 farmers in Kentucky -- the nation's top burley producer.

Tobacco-belt lawmakers have joined the debate from afar, claiming the measure would cause hardships for many farm families and infringe on trade agreements. Their objections come on the heels of historic legislation by the U.S. Congress, which bans sweetening cigarettes with flavoutrs or herbs such as clove. The bill also allows the Food and Drug Administration to regulate what goes into tobacco products.

In separate letters, U.S. Reps. Ed Whitfield and Brett Guthrie, both R-Ky., called the Canadian bill a "protectionist measure" that would violate the North American Free Trade Agreement.

Democratic Rep. Tom Perriello of Virginia wrote that protecting young people from sweet-flavoured cigarettes was "well-intended," but he objected to including American-blend cigarettes in the ban. He said the flavourings added to burley are "an important part of the manufacturing process."

The U.S. Trade Representative's office declined comment.

The biggest concern is the "potential precedence" of the Canadian proposal because so much burley is exported, said Will Snell, a University of Kentucky agricultural economist specializing in tobacco.

In recent years, total U.S. burley production has been around 200 million pounds, valued at between $1.60 and $1.75 per pound, he said. About three-quarters of that comes from Kentucky.

"So any policy that is adopted with any great magnitude worldwide that has adverse impacts on U.S. burley is a significant concern," he said.

-- With files from The Canadian Press