Analysis by Lebo Diseko, BBC News, Johannesburg
It is unprecedented for the state of the nation address to be postponed.
Making the announcement, Ms Mbete cited concerns over disruption. This was in reference to fears of possible disruption by the opposition if Mr Zuma were to give the address. And as the sitting president, he is supposed to.
All of this is happening against the backdrop of almost frenzied speculation about Mr Zuma's future.
And the one thing that has not been cancelled is Wednesday's meeting of the only African National Congress (ANC) body with the power to remove him.
If reports that the ANC is close to removing the president are true, him giving the address would have been even more awkward.
Either way this latest development has done nothing to dampen speculation in South Africa that Mr Zuma's time as president is almost up.