US Secretary of State Antony Blinken headed Thursday on a rare trip to Niger, an outpost of support for Western military operations in a region where Russia is making inroads.

Blinken will be the first top US secretary of state ever to visit the former French colony, where both France and the United States maintain forces to battle jihadists in the troubled Sahel region.

He is expected to announce more US support to Niger, one of the world's poorest countries, which returned to stability in 2011 after a history of coups.

A senior US official travelling with Blinken said the trip was meant to support the efforts of Niger under President Mohamed Bazoum, a vocal critic of Russia's Wagner Group mercenaries.

"They are making the right choices, we think, to help deal with the types of threats that are common across the Sahel. So, we are trying to highlight a positive example," the official told reporters en route to Niamey, on condition of anonymity.

She said the United States also wanted to help Niger "professionalise" its armed forces to reduce civilian casualties when responding to jihadist violence.

"Frankly, Niger is in a very difficult position," she said.

"Despite all those challenges, the leadership is really trying to do the right thing."

She also pointed to environmental threats. Niger is one of the countries most impacted by climate change, losing 100,000 hectares of arable land each year to desert.

- 'All in on Africa' -

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.

The Biden administration launched its bid for greater engagement in Africa in the face of rising investment by China, seen as the top rising challenger to the United States, but concerns have grown more recently about Russia.

Niger's western neighbour Mali has shifted decisively into Russia's orbit, hiring the Wagner Group after French troops withdrew following a nine-year military operation that prevented a takeover by jihadists but became increasingly unpopular after successive coups.

Mali last month was one of just six countries that joined Russia in voting against a resolution at the United Nations General Assembly urging Moscow to withdraw from Ukraine on the invasion's anniversary.

Burkina Faso has also fallen out with France, although both the country's military leader and Russia have denied repeated assertions that Wagner is operating there.

Niger has since become the linchpin for French military efforts in West Africa, with 1,000 troops stationed there.

The United States also built and operates so-called Air Base 201 in the centre of the desert country that is used to fly drones for attacks and surveillance on jihadists.

- Seeking progress in Ethiopia -

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.