The District has launched a new crackdown on the sale of tobacco products to children, part of a costly strategy to avoid losing federal grant money.

The campaign will be a year-round effort and will send undercover teenagers to about half of the 1,700 stores licensed to sell tobacco in the city.

The goal is to reduce the rate of underage sales of a product that sharply increases the probability of serious health problems later, health officials say. Last year, the city sent undercover teenagers to 732 stores and found that 41.9 percent of them were able to purchase tobacco.

About 44 percent of District teenagers have tried at least one cigarette, D.C. Health Department officials said, and 3.8 percent of junior high and senior high school students surveyed for the U.S. Centers for Disease Control and Prevention described themselves as frequent smokers.

The federal Substance Abuse and Mental Health Services Administration requires states and the District to prove that storekeepers comply with laws banning the sale of tobacco products to people under 18. States must prove that 80 percent of stores tested are abiding by the law. Failure to comply reduces the size of the annual substance abuse grant, and repeatedly falling short can cut the grant further.

Last year, the District's compliance rate was only 58.1 percent, well below that allowed by the federal overseers of the program.

As a result, the federal grant this year requires the District to use $1.46 million of local funds for various programs run by the Health Department's Addiction Prevention and Recovery Administration.

The penalty for another poor performance this year would be severe, said Robert L. Johnson, APRA's recently appointed director. If the compliance rate is not brought up to 80 percent, the District grant will shrink by $2.4 million in 2005, he said.

"You're really caught between a rock and a hard place," Johnson said.

Previous annual campaigns, which began in 1997, occurred only in the summertime. This year's crew of undercover kids -- all District residents -- will work year-round in the company of D.C. police officers, who are expected to issue criminal citations to violators. The law carries maximum penalties of $1,000 and 90 days in jail for repeat offenders.

The test of compliance is simple, Johnson said. The undercover agents are under 18 and carry identification cards with their actual ages. "It's a question of, are you looking at the ID?" he said.

Vendors' excuses for failure are consistent, he said. "They say they weren't paying attention," Johnson said. "They say the kids looked over 18 when they purchased the cigarettes. That simply is not good enough."

Since April, APRA has mailed letters, brochures and videos on the program to educate the vendors and alert them that they are under scrutiny.

Several convenience store owners around the city said they are ready for the program and support the city's goals of reducing underage tobacco use. Armando Amora, manager of a 7-Eleven in Takoma Park, said his employees check everyone who looks 27 years old or younger. "We ask 99 percent of them," and about 10 customers a day are turned away for lacking proof of age, he said.

"Even if they get mad, we don't care," said Donna Chi, owner of Charlie's Corner store in the Barry Farm neighborhood of Southeast. "We don't want to be in trouble. It's not good to smoke if you're underaged, so we never sell it."

Some of the teenagers are trying to buy Phillie Blunts, said Sadik A. Ismael, owner of the Penn Branch Mini-Mart on Pennsylvania Ave. SE, referring to a kind of cigar that often is emptied out and then stuffed with marijuana. "They say, 'You know me 10 years. How can you not sell it?' They are mad at me, but I don't care. . . . They come back for soda and buy cigars from another place."