"I call for President Bazoum and his family to be immediately released, and for the preservation of Niger's hard-earned democracy," Biden said in a statement Thursday, the 63rd anniversary of Niger's independence.

"In this critical moment, the United States stands with the people of Niger to honour our decades-long partnership rooted in shared democratic values and support for civilian-led governance," he said.

Bazoum, 63, was ousted a week ago by his own guard in a coup condemned by the United States, European nations and the United Nations.

"The Nigerien people have the right to choose their leaders," Biden said. "They have expressed their will through free and fair elections -- and that must be respected."

Bazoum was feted in 2021 after winning elections that ushered in Niger's first peaceful transition of power.

He took the helm of a country burdened by four previous coups since independence from France in 1960.

The clock is ticking on a demand made Sunday by West African regional bloc ECOWAS for the coup leaders to restore Bazoum to power within a week or face the possible "last resort" of military intervention.

The leader of the coup that toppled Niger's president said Wednesday that French citizens had no reason to quit the country, but rejected international sanctions, vowing not to bow to "threats".

ECOWAS leaders have imposed trade and financial sanctions and threatened the use of force if the junta does not restore ousted President by Sunday.

Responding to the international sanctions imposed in response to the coup, General Abdourahamane Tiani said the National Council for the Safeguard of the Homeland (CNSP) "rejects these sanctions as a whole and refuses to give in to any threat, wherever it comes from".

Speaking in a televised address, General Tiani said the sanctions were "cynical and iniquitous" and designed to "humiliate" the defence and security forces and Niger, and make the country "ungovernable".

French people in Niger had never been subjected "to the least threat", he added.