They also said that a unity government would not be considered.
"The question of compromise is not on the table," Odein Ajumogobia told AFP ahead of the special summit of the 15-member Economic Community of West African States (Ecowas).
"Something like a unity government or the sort of thing we have in Kenya and Zimbabwe (is) not on the table. We are resolute that Gbagbo has to step down.
"The meeting wants to consider what options there are for him to step down on his own."
Friday's meeting of Ecowas leaders in the Nigerian capital Abuja will be their second special summit on Ivory Coast this month after having suspended the country from the group at the first gathering and called on Gbagbo to cede power.
Ajumogobia said all heads of state or government were expected at the summit, except for those from Mali and Gambia, which would likely be represented at some other level.