Giga Bokeria, a leading parliamentarian, said the government will meet force with force if the gathering turns violent.
RFE/RL's Georgian Service reports that several thousand people have already gathered for the demonstration in support of former Defense Minister Irakli Okruashvili, who was arrested on September 27 on charges of money laundering and corruption.
Members of Georgia's opposition said Okruashvili's arrest was politically motivated.
Okruashvili on September 25 accused Saakashvili of ordering murders of his political opponents.
(with material from Reuters, AFP)