A week after conceding defeat, Jammeh on Friday declared that he no longer accepted the results of the election
"The United States strongly condemns the decision by President Yahya Jammeh of The Gambia to ignore the will of the Gambian people in calling for the December 1 election to be nullified," National Security Council Spokesman Ned Price said in a statement.
"The United States appeals to all Gambians to reject violence and seek a peaceful resolution that upholds the will of the Gambian people and advances the promise of a freer, more democratic, and more prosperous Gambia."
A week after conceding defeat, Jammeh on Friday declared that he no longer accepted the results of the election, upending hopes for a peaceful political transition after his 22 years in power.
The NSC specifically called on the country's security services "to uphold their sacred duty to protect all Gambians and reject any instruction to suppress peaceful expressions of dissent."
Jammeh, a devout Muslim who seized power in 1994 in the former British colony, warned Gambians not to take to the streets to protest his decision.
Signs of a massive security ramp-up multiplied across the capital Banjul on Saturday, while the United Nations Security Council led calls for Jammeh, 51, to stand down and eschew violence.
Latest official figures gave Adama Barrow, a consensus candidate backed by a coalition of opposition groups, 43.29 percent of the vote in the presidential election, while Jammeh took 39.64 percent. The turnout was 59 percent.
Those figures reflect a correction issued Monday by election authorities, showing a slimmer-than-thought victory for Barrow, of just over 19,000 votes.