Williams was suspended for four weeks for a charge on Lions wing Anthony Watson - it was hoped he would be able to serve the ban before the Rugby Championship.
RNZI reports World Rugby has confirmed the suspension is for four matches.
Since a hearing on July 2nd, World Rugby says the disciplinary committee had been receiving and reviewing additional submissions and evidence from the player's side relating to his upcoming schedule of matches.
"The player had admitted that he committed an act of foul play contrary to Law 10.4 (g) which deals with dangerous charging, and he received the suspension of four weeks, equating to four meaningful matches as considered by the judicial committee," the committee said in a statement.
Following due consideration, the disciplinary committee has ruled that Williams' suspension will extend up to and including 19 August, which is the day of the first game against Australia.
Williams will therefore be available for the second game against Australia in Dunedin on August 26th.