"On the eve of future general elections, I have today decided to set the term of office for all elections to five years," Bongo said on Monday.
The move will require constitutional reform and a vote in parliament.
Sixty-four-year-old Bongo has been president of the oil-producing West African nation since succeeding his father, Omar, who died in 2009.
He has not said whether he will run for a third term in the 2023 race for which an exact date has not yet been set. There are currently no constitutional term limits in Gabon.
The consultations on the upcoming elections are scheduled to last until Feb. 24.
Bongo suffered a stroke in October 2018 and was flown to Morocco for medical treatment. He spent three months abroad but returned shortly after a coup attempt was thwarted in his absence.
His 2016 victory triggered clashes between police and protesters during which the parliament was torched. Estimates of the death toll from the unrest range from a few people killed to more than 50, while hundreds of others were arrested, according to U.S. democracy watchdog Freedom House.
