Attorneys general from Colorado and nine other states, major credit card companies and a federal agency agreed Thursday on a plan to prevent the illegal sale of tobacco products over the Internet.

The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, the companies and state officials agreed to work together to prevent the long unchecked use of credit cards to buy cigarettes over the Internet across state lines. The agreement is effective immediately.

The result is that virtually all credit cards will no longer participate with Web sites in the United States and internationally that sell cigarettes and tobacco products.

The concerted effort and deal between the public and private sector is important because enforcement has been difficult, even though in many states, including New York, the Internet sale of tobacco products is illegal.

The selling of cigarettes online undercuts traditional business operators, often avoids sales tax for states and localities, and can be a way for underage consumers to buy cigarettes and chewing tobacco before they turn 18.

"By working with all the major card companies, we will severely restrict the availability of the Internet retailers to make these illegal sales," said New York Attorney General Eliot Spitzer, one of the lead attorneys general in the partnership sealed Thursday.

The negotiations were also led by California Attorney General Bill Lockyer and Oregon Attorney General Hardy Myers. Part of the agreement were attorneys general from Colorado, Idaho, Louisiana, Maryland, Pennsylvania, Vermont and Wisconsin.

"This initiative is a multijurisdictional approach to protecting children from obtaining tobacco products illegally," said Colorado's Attorney General John Suthers. "Working together, this initiative will help keep tobacco products out of the hands of our children."

Suthers commended the credit card companies for agreeing to work cooperatively with law enforcement in shutting down the illegal operations.

"Too often, Internet sites cater to underage smokers," said Suthers. "I am pleased with the willingness of these financial institutions to work together with state and federal law enforcement agencies to curb the growing problem of illegal cigarette sales over the Internet."

"ATF investigations show that millions of dollars each year in illegal sales of cigarettes are diverted to fund terrorists and criminal organizations," said Michael Bouchard, ATF assistant director for field operations. "Through today's initiative, we are addressing the problem of illegal sales across multiple jurisdictions with tremendous support from the country's largest credit card companies. We welcome the help."

New York's ban on Internet cigarette sales was the first in the nation. But opponents argued the law wasn't about smoking minors, but about state tax revenue. The state's tax on a pack of cigarettes is $1.50, pushing the total price to around $5.

Lower prices are offered on the Internet and in mail-order catalogs by tax-exempt Indian merchants and retailers in states with lower taxes.

In January, a federal judge tossed out racketeering charges against a group of online cigarette sellers. New York City had sued 16 cigarette Web sites to require taxes be paid on Internet sales. The city, which estimates it loses as much as $100 million a year because of the unpaid cigarette sales taxes, continues to seek to recover $15 million.

The state attorney generals argued that Internet cigarette sales present a significant risk to public health because cigarettes sold on the Internet are much cheaper than cigarettes sold by brick-and-mortar retailers, and therefore lower prices often lead to increased smoking rates, which in turn lead to more smoking-related illnesses and deaths.

Also, while brick-and-mortar retailers check photo identifications to prevent children from buying cigarettes, the vast majority of Internet sellers have age verification systems that are inadequate, often simply requiring the purchaser to click a button stating they are of legal age, Suthers said.

Numerous studies have shown that the earlier an individual begins to smoke, the more likely it is that the person will become addicted to smoking, and thus age verification through photo IDs is essential to protect children from a lifetime of addiction and smoking-related illnesses, Suthers said.