Algeria's upper house of parliament on Sunday approved a proposal to deploy troops to neighbouring Niger to "protect energy facilities", a senator speaking on condition of anonymity told AFP.
Any overseas deployment would mark a first since Algiers sent troops to support Egypt during the 1973 Arab-Israeli war.
The legislator said 148 senators in the 174-seat body voted in favour of the move. The parliament's lower house is set to vote on the proposal later in the day, likely to approve it as well.
The rare measure from Algeria comes as Algiers and Niamey strengthen security ties after moving earlier this year to repair strained relations and following a thwarted mutiny in Niger in August.
Niger faces persistent attacks by armed groups, including in areas near the border with Algeria.
The neighbours, who share a 960-kilometre (600-mile) desert border, have agreed to deepen cooperation against jihadist violence, cross-border crime and trafficking.
"This decision marks a historic break with Algeria's doctrine of non-intervention in military conflicts beyond its borders," said Abdellah Akir, an international relations researcher.
"It's driven by the need to protect Algeria's strategic depth in the Sahel and to secure the future trans-Saharan gas pipeline," Akir told AFP.
The two countries have been working to build the Trans-Saharan Gas Pipeline (TSGP), a vast project to export natural gas to Europe from Nigeria via Niger.
'Strong signal'
Akir said the measure also sought to "send a strong signal to competing actors, including Morocco and the United Arab Emirates" - two countries with which Algiers no longer has diplomatic ties.
Geoff Porter, an analyst with the North Africa Risk Consulting group, said the move was "illustrative of a shift in Algerian policy".
Algeria "had tried to maintain its national interests and exert its regional influence through its customary means - dialogue, international law, multilateral forums," Porter told AFP.
"But in a multipolar and transactional world, those don't work anymore. Instead, Algeria moved toward more tangible means - actual physical presence."
"Algeria is still committed to its foreign policy principles," he added. "It's just demonstrating them in a new way."
Earlier this month, President Abdelmadjid Tebboune signalled the possibility of military involvement in the Sahel country.
"We will protect Niger no matter what," he said in a televised address on 3 October. "There are countries, which I will not name, that have conspired against (Niger). We stand by its side."
"Today, we have interests," Tebboune then said. "We have reached agreements (with Niger) in the oil, mining and other sectors, and some are seeking to destroy all of this overnight."
Algeria's highly unusual measure to deploy troops outside its territory requires the approval of two-thirds of its parliament, according to a constitutional amendment from 2020.
Gifted warplanes
The vote followed a visit last Wednesday by Niger's Defence Minister Salifou Modi to Algeria, where he met with Tebboune and army chief Said Chengriha.
A military cooperation protocol was signed by the two sides, according to Algerian reports, but no details were given at the time.
The move also comes months after Algiers gifted four military helicopters to Niamey.
The warplanes were deployed at the request of Nigerien authorities, the Algerian defence ministry said.
Additionally, Algeria inaugurated a 40-megawatt power plant in June intended to supply electricity to Niamey and surrounding areas.
Algeria and Niger's relations had been strained for months following Algeria's downing last year of a drone from Mali.
The incident triggered a diplomatic row, with Niger joining fellow junta-led allies Mali and Burkina Faso in recalling its ambassador from Algiers.
Algeria and Mali have since resumed diplomatic ties.
Niger has been run by General Tiani since a coup in July 2023 that toppled the elected president Mohamed Bazoum, who has been detained ever since.