The internet’s most powerful companies say they will support new measures that seek to prevent online sex trafficking.

The Internet Association, which counts Facebook, Google and Amazon among its members, had at first said the proposed US law could hurt innovation.

But in a statement released on Friday the group said it was satisfied with “important changes” made to the bill.

US senators are expected to hold an initial vote on the Stop Enabling Sex Traffickers Act (Sesta) next week.

"This important bill will hold online sex traffickers accountable and help give trafficking survivors the justice they deserve,” said Senator Robert Portman of Ohio, one of the bill’s authors.

“I’m pleased we’ve reached an agreement to further clarify the intent of the bill and advance this important legislation.”

Technology companies had been opposed to the bill because of changes it would have made to Section 230 of the Communications Decency Act, enacted in 1996.

The section represents a pillar of internet law - one which protects internet companies from the actions of its users. For example, if a person uses YouTube to break the law by showing something illegal, the user, and not YouTube, is held legally responsible. The Internet Association argued that this framework meant fledgling companies were not burdened by huge, perhaps insurmountable legal risk.

'Important changes'

The compromise that finally got the technology companies on board, after going back-and-forth since August, relates to whether a site is “knowingly” aiding traffickers on their platform. The bill now clarifies that a site needs to be "assisting, facilitating or supporting" human trafficking in order to face prosecution.

"Internet Association is committed to combating sexual exploitation and sex trafficking online and supports Sesta,” said Internet Association President Michael Beckerman on Friday.

"Important changes made to Sesta will grant victims the ability to secure the justice they deserve, allow internet platforms to continue their work combating human trafficking, and protect good actors in the ecosystem.”

Amanda Hightower, executive director at Seattle-based Real Escape from the Sex Trade (Rest), told the BBC she welcomed the news.

"With the bulk of trafficking happening over the internet, it's essential we have legislation and safeguards in place to protect victims and reduce the risk of people being sold online," she said.

"Knowing that internet giants are now joining forces with legislators to reduce the potential of trafficking gives me hope that we are heading in the right direction to stop this crime and that those who facilitate trafficking online will be held responsible."

Wording 'still too vague'

The rewritten components will protect companies that take pro-active measures to remove advertisements that enable trafficking and the sale of sex, but will pave the way for prosecutors to more effectively go after sites that allegedly allow such activity to flourish.

In the crosshairs of US law enforcement is Backpage.com, a site described by California prosecutors as a “massive online brothel” that actively encourages the sale of sex through its listings website. Backpage.com did not return the BBC’s request for comment on Friday.

Despite the changes, some corners of the technology community are still concerned about the bill’s effects. Engine, a non-profit group that pushes the interests of start-ups in Washington, said the new wording was still too vague.

“While the bill sponsors have made improvements to some of the drafting problems in the original language, the changes do not address many of the startup community's concerns,” said Rachel Wolbers, Engine’s policy director.

"The bill still creates uncertainty for platforms regarding their obligations under the law and potentially penalises startups for content that they are unaware of and cannot control."