The league body claim the decision has been taken with a view to promoting the South Africa Cup final four days after the scheduled friendly on 21 May.
Derek Blankensee, general manager of the PSL, said: "We don't allow international friendlies while the season is still on because it competes with our own events and our own sponsors.
"This is the biggest game of the season for our sponsor and we want them to get the exposure they deserve."
An invitation side, made up of players from Ajax and other Cape Town professional sides, is now scheduled to face Liverpool, although all the players are registered with the PSL.
Last year Ajax hosted Manchester United in a friendly two weeks before the start of the season.