A U.S. Senate panel Wednesday held a hearing on the global problem of human trafficking, and what the United States can do in response.

A recent U.S. State Department report estimates that between 600,000 and 800,000 people are bought, sold, or forced to cross the worlds' borders each year.

Senator John Cornyn, a Texas Republican, is chairman of the Judiciary subcommittee that is investigating the issue.

He noted the State Department report says about 15,000 people are coerced into lives of forced labor and sexual slavery here in the United States. "The stories they tell are tragic, disturbing, and heartrending," he said. "And the acts they endure are not just unconstitutional, not just criminal, but profoundly evil."

Joseph Mettimano of the Christian relief group, World Vision International, says victims of sexual slavery and trade are often children.

"Driven by supply and demand, these abhorrent practices comprise a multi-billion dollar business, and the impact on children is catastrophic: long-lasting physical and psychological trauma, disease, including HIV/AIDS, violence, abuse, drug addiction, unwanted pregnancy, malnutrition, social ostracism, poverty, and in many cases death," he added.

Mr. Mettimano says outside the United States, many factors have contributed to the increase in the commercial sexual exploitation of children, including poverty, inadequate or non-enforced laws, government corruption, lack of political will, and the low status of girls in many countries.

Another reason, Mr. Mettimano says, is the spread of HIV/AIDS, which he says has encouraged men in developing countries to seek children for sex with the erroneous belief that children are less likely to carry or transmit the disease.

Mr. Mettimano says statistics suggest that the highest concentrations of prostituted children are found in Asia and Latin America.

"For example, it is estimated that one-third of the prostitutes in Cambodia are children under the age of 18," he explained. "In Eastern Europe, Russia, Poland, Romania, Hungary, the Czech Republic experienced an increase in child prostitution as well. World Vision has learned through its work in many of these countries that the average age of a child exploited in the commercial sex trade is 14 years old, but some of these children are as young as five years old. Many of these children have acquired sexually transmitted diseases."

The United States has taken steps aimed at curbing human trafficking.

In 2000, Congress passed the Trafficking Victims Protection Act, which strengthens federal criminal slavery statutes and helps victims and encourages their cooperation so others will not suffer a similar fate.

In addition, the Bush administration has increased efforts and resources to combat such trafficking.

U.S. Attorney for the Southern District of Texas, Michael Shelby, praised the progress the Justice Department has made over the past three years. "110 defendants have been convicted or charged with trafficking related offenses, which represents a three-fold increase over the previous three-year period," he stated. "Finally, we have had 77 convictions, including 59 sex-trafficking-related convictions that have been obtained by the department during that remarkable three years."

But human rights groups say more needs to be done.

Wendy Patten of Human Rights Watch called on the U.S. Senate to ratify the Trafficking in Persons Protocol, which requires governments to make human trafficking a crime.

She also called on the United States to do more to protect victims of trafficking.

"The U.S. government should also ensure that all trafficked persons be allowed to remain in the United States throughout the duration of any criminal or civil proceedings against their abusers, and ensure full implementation of measures that enable victims who fear retaliation upon return to their home country to apply for permanent resettlement on that basis," Ms. Patten added.

Ms. Patten said that victims of trafficking need counseling, medical and psychological services, legal assistance, employment authorization and training, and safe and secure shelter.