The fight against human trafficking, which for years has focused on rescuing sex slaves and punishing their pimps and smugglers, is now seeking to compel corporations to ensure they aren't unknowingly facilitating modern-day slavery.

United States Congressman Chris Smith told a conference Wednesday inside the palazzo housing the Vatican courts that Delta Air Lines Inc. has already begun training flight attendants to spot potential victims from being trafficked and to notify police upon landing.

The conference was organized by the U.S. Embassy to the Holy See, which has been on a decade-long campaign to raise awareness of human trafficking.

Between 12.3 million and 27 million people are currently estimated to be enslaved and trafficked under promises of a better life, but forced into prostitution, manual labor or domestic servitude.

The U.S. ambassador-at-large to combat human trafficking, Luis CdeBaca, said awareness of the issue had resulted in legislation to punish traffickers and protect victims, but that the next step must involve making consumers and corporations aware.

"It will take private-sector corporations collaborating with countries across regions to trace the supply chain of cheap goods and figure out where trafficking exists and how to fight it," he said.