WASHINGTON (Reuters) - The head of the U.S. Food and Drug Administration raised concerns on Wednesday about a bill in Congress that would order the FDA to regulate cigarettes, an idea backed by public health groups and many Democrats.

FDA Commissioner Andrew von Eschenbach said the bill, which is opposed by some Republicans, “may be extremely difficult for the FDA to implement.”

“We have concerns that the bill could undermine the public health role of the FDA,” von Eschenbach said in written testimony submitted for a House Energy and Commerce subcommittee hearing on the legislation.

Von Eschenbach did not appear at the hearing.

He also raised doubts about whether the FDA would have adequate resources to enforce cigarette rules and about public expectations that FDA oversight might create.

But Democrats on the panel said that, after years of failed attempts to put cigarettes within the FDA’s purview, the time has come for action.

“Regulation of tobacco is the single most important thing we can do right now to curb the deadly toll of tobacco,” said California Democrat Henry Waxman, a key backer of the bill.

“I am convinced that, in this Congress, tobacco regulation legislation will see the light of day. We are determined it will,” said New Jersey Democrat Frank Pallone.

Major tobacco companies are closely watching the bill, including Altria Group Inc, Reynolds American Inc and British American Tobacco Industries Plc. All would be affected if it passes.

On August 1, a U.S. Senate committee endorsed a similar bill with the support of health groups and Altria’s Philip Morris, the nation’s largest cigarette maker.

Since then, the bills have picked up significant bipartisan support on Capitol Hill. The House measure now has 200 co-sponsors, while the Senate version has 55.

At the hearing, nonetheless, some Republican lawmakers raised concerns similar to von Eschenbach’s.

“We ought to take a step back and really think about it ... You can’t just keep piling more and more work on the FDA without giving the agency additional resources,” said Texas Republican Joe Barton.

Another Texas Republican, Michael Burgess, said he opposes smoking, but questioned putting the FDA in charge of regulating a product that is inherently unhealthful.

“Why are we going to waste taxpayer dollars to regulate a product like this? What do we got next in line? Crystal meth?,” Burgess said.

The House bill would enable the FDA to police cigarette labeling, restrict their sales, prohibit flavored cigarettes and recall tobacco products seen as unreasonably harmful.

The FDA would also have to approve all new cigarettes and other tobacco products, and set standards for so-called reduced-risk products. The agency would not be empowered to ban cigarettes or require nicotine levels of zero under the bill.

Waxman said: “Tobacco is different from other products regulated by the FDA ... FDA needs new resources to do the job and that’s why we have a user fee in the bill.”

Tobacco companies would fund the FDA’s oversight of their industry under the House bill through hundreds of millions of dollars in user fees likely to raise the price of cigarettes.

Smoking is the number one preventable cause of death in the United States, leading to more than 400,000 deaths and $96 billion in health care costs each year, health groups say.