The appeal from Cynthia Akuetteh came as the political situation in Gabon has become increasingly tense, with opposition to President Ali Bongo Ondimba growing sharper.
“Calls for insurrection or for violence are abhorrent and unacceptable,” the ambassador said in a statement. “Rather, all sides should commit themselves to open and inclusive dialogue.”
She said the United States would “strongly condemn any attempts to change government through extra-constitutional means”, saying any change should come through “democratic” means.
“Gabon has long been a model of stability in a fragile region,” she added.
Ali Bongo assumed the presidency following 2009 death of his father Omar Bongo, who had ruled the nation since 1967.
Rising popular anger over the one-family rule as been further sharpened by the widening wealth gap in oil- and mineral-rich Gabon.
Last month, a banned march demanding Bongo’s ouster ended in clashes between protestors and police, which authorities say led to the death of a demonstrator, but opposition leaders blame for six fatalities.
Around 100 protesters were arrested during the march, and their trial for various offences started last week.
On Monday, the Libreville home of Gabonese opposition figure and former African Union commission president Jean Ping was attacked by a gang of around 200 youths, who Ping says were paid by authorities to mount the assault.
After what Ping said was a refusal by police to intervene, opposition supporters halted the attack, and detained around 15 people.
Gabon’s defence ministry complained that one of those held was a plain clothes intelligence agent who it said was on an official mission to safeguard the French community in the wake of last week’s attacks in Paris.