Mikheil Saakashvili, who is based in Ukraine, says he plans to return to Georgia to help "save the country".
Georgian authorities say they will arrest former President Mikheil Saakashvili if he returns to the country.
Saakashvili announced on Monday that he planned to fly to Georgia for the weekend's local elections.
The 53-year-old, who served as president from 2004 to 2013, has been accused by the Georgian judiciary of abuse of power.
The founder of the main opposition United National Movement (UNM) party has been living in exile in Ukraine.
He states that the case is political and posted a photo on Facebook of a plane ticket to Tbilisi for Saturday night's vote.
"I will be in Tbilisi to protect your electoral choice with you," Saakashvili said in a video.
His potential return to Georgia is seen as a significant test for the country's ruling Georgian Dream party.
But Prime Minister Irakli Garibashvili assured on Tuesday that if Saakashvili "sets foot on Georgian soil, he will be immediately arrested and imprisoned".
Georgia was plunged into a political crisis since last year when opposition parties claimed there was massive fraud in the parliamentary elections.
In May, European Council President Charles Michel brokered an exit agreement, but the Georgian Dream unilaterally pulled out after two months, drawing criticism from the EU and the US.
In his video message, Saakashvili insisted that the agreement must be respected, calling Saturday's local elections a "referendum" against the Georgian Dream.