The former All Black has been suspended from Paris club Racing 92 over a suspected drug deal involving Australian international James O'Connor.
Williams was charged with buying cocaine and O'Connor with possession of the drug after French police arrested the pair outside a Paris nightclub on Sunday.
France correspondent Catherine Field told Newstalk ZB that French media reported Williams has made a plea bargain and will appear before a judge and a prosecutor later this week in a closed court.
Meanwhile, the French Rugby Federation has reportedly made moves to ban Williams from playing rugby in the country.
Field said, according to French media reports, the organisation that oversees French club rugby had started proceedings against Williams, saying he had brought the game into disrepute.
