Esper, the first defense secretary to visit Algiers in almost 15 years, hopes "to deepen cooperation with Algeria on key regional security issues, such as the threat posed by extremist groups," a senior US military official said.

Esper, due in the country as part of a North Africa tour, will arrive in Algiers after talks in neighbouring Tunisia, before heading to Morocco.

"Algeria is a committed counter-terrorism partner," General Stephen Townsend, head of US Africa Command, said on a recent visit to Algiers.

US military officials frequently visit Tunisia and Morocco, where defence cooperation with Washington is well established.

But Esper will be the first defense secretary to visit Algeria, an ally of Russia and China, since Donald Rumsfeld in 2006.

He is expected to be received Thursday by Algerian President Abdelmadjid Tebboune -- who is also defence minister and head of the armed forces -- and with the Chief of Staff, General Said Chanegriha.

"Strengthening this relationship is very important to us," Townsend said.

"Degrading violent extremist organisations... and enhancing regional stability is a mutual must."

- 'Pivotal state' -

Algeria is trying to reactivate its role on the regional diplomatic scene, including as a mediator in the conflicts in Mali and Libya.

Jihadist groups in Libya and the wider Sahel region have become an increasing concern since a NATO-backed uprising toppled and killed longtime dictator Moamer Kadhafi in 2011.

Conflict in Libya since then has sucked in multiple nations backing opposing forces, including Turkey and Egypt.

Mali, supported by France and UN peacekeepers, is struggling with an eight-year-old Islamist insurgency that has claimed thousands of lives.

"The Americans want to reposition themselves in the region, which has seen the arrival of new players like Turkey," said Algerian political scientist Mansour Kedidir.

"Algeria has always been considered by the Americans as a 'pivotal state' whose vulnerability can engulf the whole region if it is affected by jihadists."

The US and Algeria have historic ties -- a treaty of friendship was signed in 1795 -- while during the 1954-1962 war of independence from colonial rulers France, Washington reportedly pressured Paris to negotiate with Algerian nationalists.

"The United States has a strong bilateral security relationship with Algeria that dates at least to the early days of the Global War on Terror," said Michael Shurkin, from the California-based RAND Corporation policy think-tank.

"Their partnership has regional implications."

Algeria was one of the first countries to offer the US support after the 9/11 attacks in New York.

But the US relationship is crucial for another reason, Shurkin noted.

"The US role must also be seen in the context of Algeria's reluctance to work with France, which makes the US necessary for France with respect to French hopes for an integrated regional response to jihadism," Shurkin said.

France has 5,100 soldiers deployed across the Sahel as part of its anti-jihadist Operation Barkhane.

Washington is also likely interested in selling weapons to Algeria, which currently receives some 90 percent of its supplies in this segment from Russia.

Just ahead of Esper's planned visit, Chanegriha met with a top Russian military delegation for discussions on the state of "military cooperation between the two countries," Algeria's defence ministry said in a statement.

Kedidir, the political scientist, said Esper's visit was only a first step for the US.

"It's a long-term job that cannot be settled in one visit," he said.

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