Badri Patarkatsishvili said in a statement from abroad that he would run in the Jan. 5 vote if the fragmented opposition is unable field a single candidate.
"The West, particularly the United States , carries a special responsibility. I'm asking the nations friends of Georgia to help protect democracy," Patarkatsishvili said Sunday.
"Now not only Georgians, but the entire world has realized what democracy in Saakashvili style means.
Patarkatsishvili is seen as a driving force behind anti-government protests in Georgia that led Saakashvili to introduce a 15-day nationwide state of emergency on Wednesday, hours after police clubbed and tear gassed opposition protesters in the capital, Tbilisi . Independent broadcasters' news reports have been taken off the air, which opposition leaders claim prevents them from campaigning.
The incidents have raised doubts about the U.S.-allied Saakashvili's commitments to democracy and drawn strong criticism in the West.
Saakashvili, who sought to shed Russia's influence and integrate Georgia into the West, has defended the crackdown on protesters and the state of emergency order as a necessary response to what he described as a coup attempt staged by Moscow. Russia angrily rejected the allegations and the Georgian opposition denied having any links to the Kremlin.
Georgian authorities on Wednesday evicted three Russian diplomats on spying charges. Russia dismissed Saakashvili's accusations and responded by expelling three Georgian diplomats.
Patarkatsishvili said he would run for president "to offer an alternative amid an unprecedented blackmail and harassment of the opposition by Saakashvili's regime."
He said his main campaign motto is: " Georgia without Saakashvili is Georgia without terror," and promised to turn over most presidential powers to parliament if elected.
Patarkatsishvili, who built a fortune in Russia during the 1990s and returned to his native Georgia in the early years of this decade. He initially had good relations with authorities, but had a falling-out with the government in 2006 over business disputes and other issues.
It was unclear whether Patarkatsishvili would be able to campaign. He is believed to be in Israel , and prosecutors said he was under criminal investigation for plotting to overthrow the government.
In his statement, Patarkatsishvili urged the government to close criminal cases against him and other opposition figures. "Adding to the state of emergency and muzzling of the media, they have tried to block opposition candidates from running by casting them as 'enemies of the people,"' he said.
Opposition groups have complained that the ban on independent TV news broadcasts will deny them media access when they already have little time to campaign. Envoys from the Parliamentary Assembly of the Council of Europe urged Saakashvili to allow broadcast media to resume operations.
Patarkatsishvili founded the Imedi television station, which was regarded by authorities as an opposition mouthpiece and was raided by riot police late Wednesday. He recently handed over control of Imedi to Rupert Murdoch's News Corp.
Lewis Robertson, an American who is the channel's director, told The Associated Press that troops which raided the station broke its equipment and it could take several months to get the station back on the air.
The violent dispersal of opposition rallies and Saakashvili's emergency order drew sharp criticism from the West and warnings that it could harm efforts to integrate this small Caucasus nation into the European Union and NATO.
A senior U.S. diplomat, who was scheduled to meet with Saakashvili and opposition groups Sunday, said he would express concern about the violence that forced independent television channels off the air.
"The reports that we are starting to get now are that things went beyond a textbook policing operation," Deputy Assistant Secretary of State Matthew J. Bryza told the AP. "We are hearing more and more reports that people were grabbed from stores or that passers-by were beaten. Things got out of control."