The Federal Trade Commission and Facebook are negotiating over a multi-billion dollar fine that would settle the agency’s investigation into the social media giant’s privacy practices, according to two people familiar with the probe.

The fine would be the largest the agency has ever imposed on a technology company, but the two sides have not yet agreed on an exact amount. Facebook has expressed initial concern with the FTC’s demands, one of the people said. If talks break down, the FTC could take the matter to court in what would likely be a bruising legal fight.

Facebook confirmed it is in discussions with the agency but declined to comment further. The FTC declined to comment. The two people familiar with the probe spoke on the condition of anonymity because they were not authorized to discuss the private talks.

“Facebook faces a moment of reckoning and the only way it will come is through an FTC order with severe penalties and other sanctions that stop this kind of privacy misconduct going forward,” said Democratic Sen Richard Blumenthal (Conn.).