The new rule, which officials said would be announced on Tuesday, means that six relatively rare forms of E. coli will be treated the same as their notorious and more common cousin, a strain called E. coli O157:H7. That strain has caused deaths and illnesses and prompted the recall of millions of pounds of ground beef and other products. It was banned from ground beef in 1994 after an outbreak killed four children and sickened hundreds of people.

“We’re doing this to prevent illness and to save lives,” said Dr. Elisabeth Hagen, the head of food safety for the Agriculture Department, which regulates meat. “This is one of the biggest steps forward in the protection of the beef supply in some time.”

It is not illegal to sell fresh meat or poultry containing most toxic bacteria, like salmonella; they are frequently found on groceries’ meat, and thorough cooking typically kills the pathogens. But since the 1994 outbreak, which involved hamburgers served at Jack in the Box restaurants, regulators have treated E. coli in ground beef differently.

Many people eat rare or undercooked ground beef, and if it is tainted, resulting illnesses can be deadly. Toxic E. coli, in its most common O157 form, is so virulent that just a few organisms can make people violently sick. The toxic E. coli live in the digestive tracts of cows and can get on meat during slaughter. It can cause bloody diarrhea, stomach cramps and, in severe cases, kidney failure.

In recent years, scientists found that several other strains of E. coli in food were also making people sick, and they identified the six most potent, called the Big Six non-O57s. Beginning at least four years ago, the U.S.D.A. began considering extending its ban to those additional toxic strains.

But the American Meat Institute, an industry group, has argued that safety measures already in place are sufficient. On Monday, the group was highly critical of the extended ban.

“Imposing this new regulatory program on ground beef will cost tens of millions of federal and industry dollars — costs that likely will be borne by taxpayers and consumers,” the group said in a statement. “It is neither likely to yield a significant public health benefit nor is it good public policy.”

While several outbreaks caused by the Big Six strains have been linked to produce, the group pointed to the fact that only one has been related to ground beef. In that outbreak, last year, three people fell ill.

“It’s just not supported by the science,” James H. Hodges, the institute’s executive vice president, said in an interview.

The Centers for Disease Control and Prevention estimate that E. coli strains other than O157:H7 cause nearly 113,000 illnesses each year, one-third of which can be attributed to tainted beef, according to U.S.D.A. officials. Until recently, few cases were reported, however, because most medical labs were not equipped to test for the less common forms.

The Agriculture Department will begin enforcing the rule in March, to give the meat industry time to prepare. The rule will apply to hamburger meat and trim or beef scraps that go into it, as well as some other products, like steaks that have been tenderized with machines that use needles to poke minute holes in the surface. Some meat processors have begun to test for the six strains in recent months in anticipation of federal action, and many others will most likely begin testing once the government begins its own testing.

Under the rule, raw meat containing the Big Six E. coli cannot be sold to the public. Currently, most packing plants divert meat containing E. coli O157:H7 for use in cooked products, and will most likely do the same with meat containing the new strains, as well. The bacteria is killed by heating the meat to 160 degrees.

While the new rule significantly expands the Agriculture Department’s beef ban, it does not include all forms of toxic E. coli. A highly virulent strain of the bacteria that caused dozens of deaths among people who ate contaminated sprouts in Europe this summer is not one of the Big Six because it has not been detected as a cause of illness in the United States.

Dr. Hagen said the list of banned pathogens might grow. “This is where we started and it doesn’t rule out the possibility that we would consider other pathogens in the future,” she said.

The new rule highlighted the patchwork and often confusing nature of food safety regulation, where most meat is under the jurisdiction of the U.S.D.A. while most other foods, including produce, are regulated by the Food and Drug Administration. The F.D.A. already considers it illegal to sell food containing any bacteria, including toxic forms of E. coli or other substances that could make people sick.

Dr. Hagen also said the rule did not conflict with the Obama administration’s push to cut back on regulation that could increase costs for business at a time of economic hardship.

“There’s really no inconsistency between having a strong economy and having a safe food supply,” Dr. Hagen said. The U.S.D.A. estimated that the rule would cost the industry up to $10 million a year for testing and holding meat back from the fresh ground beef market.

“The amount this is going to cost is insignificant compared to the lives that will be saved,” said Senator Kirsten E. Gillibrand, Democrat of New York, who pushed for the expanded rule.

After the U.S.D.A. banned the O157 form of E. coli from ground beef in 1994, the meat industry sued to block the move, but the agency prevailed in court.

Mr. Hodges, of the meat institute, said the group had yet to see a full version of the rule and would consult with its members before deciding how to respond.

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