WASHINGTON, Aug 8 (AFP) - United States is seeking to prevent Russia from scoring a major new win with coup-hit Niger, wagering despite initial disappointment that long-standing military ties will keep the country in the Western orbit.

Niger has been the linchpin of US and French anti-militant operations in the Sahel, especially since the military takeover of neighbouring Mali, which has shown the door to Western forces and welcomed Russia's ruthless Wagner mercenary force.

Victoria Nuland, the acting deputy secretary of state, on an unannounced visit to Niamey on Monday acknowledged little progress on reversing the Jul 26 coup but said that the military leaders "understand very well the risks to their sovereignty when Wagner is invited in".

She said that her main interlocutor, the newly named military chief of staff Brigadier General Moussa Salaou Barmou, has worked closely with US Special Forces and that she went into detail on "aspects of our cooperation that he has historically cared about a lot".

"So we are hopeful that that will sink in," she said.

Secretary of State Antony Blinken just months earlier paid a highest-ranking visit ever by a US official to Niger. He saluted gains under the elected president, Mohamed Bazoum, who was an honoured guest both at democracy and Africa summits thrown by President Joe Biden.

US policymakers see no Russian hand in the coup but point to Russian influence operations since then, including French-language social media postings and rallies in support of the military takeover.

Playing on resentment of former ruler France, Wagner chief Yevgeny Prigozhin in a purported audio message hailed the coup as "nothing more than the struggle of the people of Niger against colonisers".

In an interview with the BBC, Blinken said that Bazoum's ouster was "not instigated by Russia or by Wagner", but warned that Wagner would "try to take advantage of it".

State Department spokesman Matthew Miller brushed aside suggestions of pro-Moscow sentiment after Russian flags appeared in demonstrations in Niger.

"I think it's very strange that if your country is taken over by a military junta and you want to show your support, the way you decide to do that is by running out and buying - I guess at a store locally - a Russian flag," Miller said.