Kansas City, Mo. ? Kristy Childs was in sixth grade the first time she helped a man undress for sex.

The frightened 12-year-old had climbed into the semi-truck hoping for a ride somewhere — anywhere — far away from a home where her stepfather had been sexually abusing her.

But the truck driver, who gave her a ride, something to eat and a place to sleep, made her have sex with him to pay him back. For Childs, giving in to him seemed somehow better than having the same thing happen to her at home. Over the years she was arrested too many times to count for prostitution. Her customers, however, walked free without facing any criminal charges.

Now the Justice Department is starting to go after those who pay to have sex with children. Previously authorities targeted people who sold children for sex, but they are taking advantage of a little-used provision of a 2005 bill to focus their efforts so far in Kansas and Missouri after noticing an apparent rise in child prostitution cases.

In Kansas City, a sting dubbed Operation Guardian Angel this year resulted in guilty pleas by six men who answered Internet ads for sex with underage girls. After a similar sting in St. Louis, two men in St. Louis pleaded guilty to attempting to obtain a minor for sex, and a Catholic priest is awaiting trial.

“We became aware of the alarming market for child sex trafficking while successfully prosecuting several cases of child prostitution,” said Matt Whitworth, acting U.S. attorney in Kansas City. “As we obtained convictions against the pimps in those cases, we realized an aggressive strategy was needed to attack this issue on all fronts.”

The federal Trafficking Victims Protection Act, enacted in 2000, intially on international human trafficking. But in 2005, Congress revised it to include domestic trafficking, including the sex trafficking of children.

It estimated that “as many as 300,000 children in the United States are at risk for commercial sexual exploitation, including trafficking, at any given time.”

Though federal prosecutors have had the authority to go after customers of the domestic child sex trade for the past decade, none had used the act in that way.

That changed when assistant U.S. Attorney Cynthia Cordes, who earlier this year used RICO statutes for the first time to prosecute a human trafficking case, began focusing on the demand for underage prostitution.

“We became the first district in the nation to take advantage of provisions of the Trafficking Victims Protection Act to target the customers of child prostitutes,” Whitworth said. “Other districts are now successfully following the same strategy. We are prosecuting not only those who recruit children into prostitution, but also their customers who create the demand for child sex trafficking.”

Linda Smith, head of Shared Hope International, said the Missouri efforts were a success because prosecutors were able to prove the intent of the men who had offered to pay for sex with a child.

“The fact that (Cordes) stayed with it, got prosecutions, they got the prison time, that has rippled around the United States,” Smith said.

Shared Hope, a Vancouver, Wash.-based organization created to rescue victims of sex trafficking, conducted a two-year study that concurred with the government report that up to 300,000 underage American girls are sexually exploited every year.

It’s not always strangers victimizing them. Last month a woman in North Carolina was charged with prostituting her 5-year-old daughter, who is believed to have been killed by a man accused of raping her. In Kansas City, a man and woman pleaded guilty in September to training the woman’s 12-year-old as a sexual dominatrix and using the Internet to sell her as a prostitute.

“These are middle school kids,” said Smith, a former U.S. congresswoman who started Shared Hope in 1998. “Most of them are missing kids. We’ve found them in strip clubs, being delivered to motel rooms. They’re not lost. They’re being consumed by the hour by pretty ordinary men in America.”

As awareness of the sex trafficking problem grows, officials say more is being demanded of the government to fight it.

“Federal statutes provide a heavy hammer with tough mandatory prison sentences for both buyers and sellers who victimize children,” Whitworth said.

Childs, who settled in the Kansas City area and formed an advocacy group for victims of sex trafficking, says it was “a great step” for authorities to use the federal law the way they did.

The Associated Press generally doesn’t identify victims of sex abuse, but Childs agreed to go on record for this story and frequently speaks in public about her experiences as a child sex trafficking victim.

Now in her late 40s, Childs can’t remember whether she got into the truck that first time at a truck stop or somewhere along the roadside. That first ride led to a second, then dozens more.

“The truckers would CB each other, so I wouldn’t even have to get back out on the road,” Childs said. “I could just go from one truck to another truck and be headed off in another direction. I wasn’t getting any money. It was survival sex.”

Childs formed Veronica’s Voice in 2000 to help girls and women break away from prostitution, and has shared her story with thousands of prostitutes in the Kansas City area.

Despite the increased attention being given to domestic child sex trafficking, Childs said the government is not moving fast enough to help with services for victims.

Veronica’s Voice receives no government subsidies, she said. Instead, the group relies on donations to fund its $100,000 a year budget, which pays for three full-time employees, rent, utilities and the cost of providing services to clients.

“We have millions of dollars going to other countries to fight this issue,” Childs said. “I think anyone who is in sexual slavery who wants out, regardless of how they got there, deserves the opportunity and the services to help get them out.”