US actor and tech investor Ashton Kutcher has made headlines for his emotional testimony, about the work of his anti-trafficking foundation, at a US Senate hearing on modern slavery in Washington.

Key points: Kutcher wants government support for development of new technology to fight sex trafficking

Kutcher wants government support for development of new technology to fight sex trafficking Actor was speaking to Senate hearing examining US role in ending modern slavery

Actor was speaking to Senate hearing examining US role in ending modern slavery Kutcher is chairman of Thorn, a non-profit that has created technologies to help identify abuse victims

Kutcher urged US legislators to drum up government support for the development of new technology to fight online sex trafficking.

The actor and philanthropist was close to tears when he talked to the US Senate Foreign Relations Committee about what his foundation Thorn: Digital Defenders of Children does.

The Senate hearing, Ending Modern Slavery: Building on Success, examined progress the US is making in global efforts to end modern slavery and human trafficking.

It follows heightened scrutiny of classified advertising websites such as Backpage.com for carrying ads that offer children for commercial sex.

"Technology can be used to enable slavery, but it can also be used to disable slavery," Kutcher said.

He spoke as chairman of Thorn, a tech non-profit that has produced web-based tools to help police officers identify and locate victims of trafficking.

"I've been on FBI raids where I've seen things that no person should ever see.

"I've seen video content of a child that is the same age as mine being raped by an American man that was a sex tourist in Cambodia. And this child was so conditioned by her environment that she thought she was engaging in play.

"I've been on the other end of a phone call from my team asking for my help because we had received a call from the Department of Homeland Security telling us that a 7-year-old girl was being sexually abused and that content was being spread around the dark web and she'd been being abused and they'd watched her for three years and they could not find the perpetrator. Asking us for help.

"We were the last line of defence, an actor and his foundation were the potential last line of defence."

Thorn technology used worldwide to fight online slavery

During his appearance in the Senate, Mr Kutcher explained that the "tools" Thorn has created, called Spotlight and Solis, are vital in achieving these goals and can be used by law enforcement to prioritise their case load.

The Spotlight tool, which Kutcher said has helped identify 6,000 victims in six months, was created after a 2012 sex trafficking survey found that 63 per cent of underage victims reported being bought or sold online.

The Solis tool, Kutcher said, is currently being used by 40 agencies across the world today in beta and he expects the tool will "get smarter and more efficient and cost effective over time".

Kutcher, who is married to actress Mila Kunis and has two children, co-founded Thorn in 2010 and said becoming a parent had propelled his crusade against trafficking.

"The right to pursue happiness for so many is stripped away, it's raped, it's abused, it's taken by force, fraud or coercion — it is sold for the momentary happiness of another," the 39-year-old said.

"My other day job is that of the father of two — a two-month-old and a two-year-old — and as part of that job, that I take very seriously, I believe that it is my effort to defend their right to pursue happiness and to ensure a society and government that defends it as well."

Each year, up to 300,000 children are at risk of being trafficked for commercial sex in the United States, according to the US Department of Justice.

Most sex trafficking victims are advertised or sold online, according to a US Senate subcommittee report that was released last month.

The actor's testimony comes ahead of the upcoming annual Shine a Light on Slavery Day, on 23 February.