President Bush signed a bill Tuesday to combat human trafficking, saying thousands of teenagers and young girls are brought to the United States each year and "forced to submit to unspeakable evil."

The bill renewed the Trafficking Victims Protection Act of 2000, the first comprehensive federal law for prosecution of traffickers. The Justice Department reported late last year that it had prosecuted 277 traffickers since 2001 and obtained convictions in every case. An estimated 75 percent of the prosecutions involved sex trafficking.

Victims have been found in brothels, bars, sweatshops, clandestine factories, restaurants, massage parlors and even private homes where women and girls are kept in servitude.

"It takes a perverse form of evil to exploit and hurt those vulnerable members of society," Bush said.