Representing Gabon before the UN, Ndong Sima promised that he would announce next week steps toward holding new elections.
Gabon's military-installed prime minister on Friday defended the takeover before the United Nations as a "lesser evil," saying the intervention prevented bloodshed.
Military leaders on August 30 overthrew Ali Bongo Ondimba, whose family has ruled the oil-rich Central African state for more than half a century, just as he was proclaimed the winner of another term.
The military installed Raymond Ndong Sima, who had run against Bongo in the latest election, as a transitional prime minister.
Representing Gabon before the United Nations, Ndong Sima promised that he would announce next week steps toward holding new elections.
He called on the international community not to speak "without nuance" on the coup and instead to look at the situation in Gabon, where the Bongo family has been accused of rampant corruption.
"To condemn such an event would be to say it's better to let clashes take place and then count the number of victims, because no one in the opposition was willing to let this umpteenth heist go ahead," Ndong Sima said of Bongo's declared election victory.
"Security forces had the choice between preparing to repress the protests, with the risk of being held accountable now or later before international courts or deciding to stop this fraudulent and dangerous process for the sake of national cohesion," he said.
"They chose with full responsibility the second path to prevent the risk of a fire that could have shaken the very foundations of Gabonese society and would not have spared the numerous foreign communities living in Gabon," he said.
"This intervention without any blood or damages was the lesser evil," he said.
Ndong Sima, a French-educated economist who had earlier served as prime minister under Bongo, also represented Gabon in the Security Council, where the country holds a non-permanent seat.
At a session Wednesday on Ukraine attended by President Volodymyr Zelenskyy, the military-installed Gabonese prime minister called for negotiations to end the war.