Blinken's visit to Niger, the first by a U.S. Secretary of State, signals its importance as a U.S. ally in the Sahel, a senior State Department official stated.
The United States built and operates so-called Air Base 201 in the center of the desert country that is used to fly drones for attacks and surveillance on jihadists.
Aides to Blinken hope his visit will encourage the consolidation of democracy in Niger, which returned to elected rule in 2011 after a history of coups.
President Mohamed Bazoum has won praise in Washington, including at a summit for African leaders thrown by Biden in Washington in December.
Speaking Wednesday on a visit to Ethiopia, Blinken said his trip to the two countries was part of President Joe Biden's pledge to be "all in on Africa, and all in with Africa".
"That means the United States is committed to deep, responsive and genuine partnerships on the continent," Blinken told reporters.
Blinken started Thursday with talks in Addis Ababa with the leadership of the African Union, part of the Biden administration's effort to show deference to the region and avoid perceptions of an overbearing US role.
African Union-led negotiations, backed by US diplomats, brought about a November 2022 ceasefire that has largely ended the brutal two-year Tigray war in Ethiopia.
After talks Wednesday with both Ethiopian Prime Minister Abiy Ahmed and Getachew Reda, a senior leader of the Tigray People's Liberation Front (TPLF), Blinken said the peace deal was largely holding with a "very significant drop" in abuses.
But he called for accountability for past abuses in the war, where he had earlier alleged human rights violations and where the United States estimates some 500,000 people may have been killed over two years - well above the toll from Russia's invasion of Ukraine.
The Tigray war had set back the historic US relationship with Africa's second most populous nation, with Abiy voicing anger over the abuse allegations and the US suspension of key trading privileges.
But Finance Minister Ahmed Shide sounded reconciliatory as he spoke Wednesday next to Blinken, who announced $331 million in new food and other emergency aid for Ethiopia.
The minister said Abiy's government wanted an "inclusive national dialogue" to address grievances.
"Mechanisms for transitional justice are also being set up to ensure justice and accountability to end perpetual acts of violence and avert impunity," he said.