The Polisario had already announced last month that it regarded a 1991 ceasefire as over
Algeria's prime minister yesterday criticized "foreign manoeuvres" he said were aimed to destabilize it, after Washington recognized Morocco's sovereignty over Western Sahara in exchange for Rabat normalizing ties with Israel.
Algeria, Morocco's neighbour and regional rival, is the key foreign backer of the Polisario Front, which has campaigned for independence for Western Sahara since the 1970s.
"There are foreign manoeuvres which aim to destabilize Algeria," Prime Minister Abdelaziz Djerad said, in Algeria's first reaction to the US decision.
"There is now a desire by the Zionist entity to come closer to our borders", he added, in reference to Israel.
"We are seeing today at our borders... wars and instability around Algeria," Djerad said, in a speech to mark the anniversary of demonstrations against French colonial rule.
The surprise announcement by outgoing President Donald Trump on Thursday of US recognition of Moroccan sovereignty over Western Sahara was swiftly dismissed by the Polisario, who have vowed to fight on until Moroccan forces withdraw.
The Polisario had already announced last month that it regarded a 1991 ceasefire as over, after Morocco sent troops into a UN-patrolled buffer zone to reopen the road to neighbouring Mauritania, Morocco's sole land link to sub-Saharan Africa.
The Polisario has since claimed that repeated exchanges of fire have taken place along the 2,700-kilometre sand barrier that separates the two sides.
The Sahrawi Arab Democratic Republic (SADR), which Polisario leaders proclaimed in 1976, is a member of the African Union, but controls just 20 percent of the territory, mostly empty desert.
The territory's main sources of revenue -- its phosphate deposits and rich Atlantic fisheries -- are all in Moroccan hands.
As a result, the Polisario is heavily dependent on support from Algeria, where it operates rear-bases and runs camps for tens of thousands of Sahrawi refugees.
For the Polisario, Algeria's support would be essential for any return to major fighting.
The US move sparked fears in Algeria that Morocco's deal will allow Israeli forces to operate along its frontier.
"The Israeli army is at our borders," Algerian journalist and analyst Abed Charef wrote.
"The rapprochement between Morocco and Israel opens the way, if it has not already happened, for Israeli aid to support Morocco's army."
Algeria's military magazine, El-Djeich, called in its December editorial for Algerians to "stand ready to face" imminent threats.
It warned of a "deterioration of the regional situation along our border and the threat that certain enemy parties pose."
Last month, Algeria approved constitutional changes including to the mandate of the military, one of the most powerful in the region.
The changes allow the army to potentially carry out "peacekeeping" operations in neighbouring countries, which include war-ravaged Libya and Mali.
Algerian political scientist Mansour Kedidir warned that if Israel does establish a presence along the frontier it would be a "provocation."
But he added that US recognition did not necessarily change the situation on the ground in Western Sahara, which was in the hands of the United Nations.
The UN -- which has its Minurso mission in Western Sahara -- said its position on the territory was "unchanged."
UN Secretary-General Antonio Guterres believed "the solution to the question can still be found based on Security Council resolutions," his spokesman said.
And Secretary of State Mike Pompeo said on Friday that the United States still favoured a diplomatic solution to the Western Sahara dispute, despite Trump's recognition of Moroccan sovereignty.
"The United States continues to believe only political negotiations are capable of resolving the issues between Morocco and the Polisario," Pompeo said in a statement