An outburst of hostile rhetoric between Morocco and Algeria reflects a historic animosity rooted in irreconcilable differences over Western Sahara, with analysts saying political factors are reinforcing the deadlock despite some much-needed cooperation.
The decades-old rivalry between the Maghreb neighbours has resurfaced after Algeria's ageing President Abdelaziz Bouteflika, in power for 13 years, suffered a mini-stroke and with Morocco's coalition government on the brink of collapse.
Comments by Algeria's foreign ministry, linking the normalisation of ties to progress on drug trafficking and the Western Sahara dispute, prompted Morocco to "vigorously denounce" what it called "unacceptable" conditions.
Last week Rabat branded Algeria's political culture "obsolete" and "totally out of sync with the demands and views of the 21st century," while Algiers accused Morocco of deliberately escalating an anti-Algeria media campaign.
Maghreb expert Khadija Mohsen-Finan said the intransigent language on both sides could be explained by the uncertainty over Bouteflika, who has been hospitalised in France since April, and the unresolved political crisis in Morocco.
"We can see nationalism emerging in both countries and revolving around the issue of the border and the Western Sahara. I think there's a certain amount of agitation going on in the domestic political arenas," she said.
The war of words is not new for the regional arch-rivals, which despite shared language and culture are defined by radically different post-colonial politics.
Morocco annexed the phosphate-rich Western Sahara in 1975, in a move never accepted internationally.
And Algeria, which says it is not a party to the conflict, backs the pro-independence Polisario Front which fought for a separate state until the UN-brokered ceasefire in 1991.
The latest ruckus comes almost exactly 50 years after Morocco invaded Tindouf in western Algeria, now home to Polisario-run Sahrawi refugee camps, with the so-called Sands War in October 1963 sowing the seeds of animosity that has hampered relations ever since.
Algiers blamed the angry exchange on comments made two months ago by Hamid Chabat, leader of the nationalist Istiqlal party, who threatened to pull out of Morocco's ruling coalition. He claimed Tindouf belonged to Morocco and that Moroccans wanted it back.
But the spat has dimmed any chances of reopening the 1,600-kilometre (1,000-mile) shared border, despite a deepening economic crisis giving Morocco a powerful incentive to mend ties and boost trade with its energy rich neighbour.
The vast desert has been closed at considerable cost to both sides since 1994, after an attack in Marrakesh which Rabat blamed on Algerian intelligence.
Moroccan economist Fouad Abdelmoumni estimates the cost of the Maghreb region's "non-integration" at around 2.2 percent of GDP, and as much as 4 percent in lost growth outside the non-hydrocarbons sector.
"The loss is huge," he said.
"Clearly the cost of running our states, particularly our armies, the cost of the conflict in the Sahara, the cost of subsidies... neither country can afford the luxury of remaining in this logic."
Military budgets have grown sharply over the past five years, according to the Stockholm International Peace Research Institute (SIPRI), with Algeria's expenditure reaching 9.3 billion dollars in 2012, a rise of 73 percent from 2008, and Morocco spending around 3.4 billion dollars.
William Lawrence, International Crisis Group's North Africa director, says a deal on reopening the Algeria-Morocco border is feasible, as long as Western Sahara is kept out of the negotiations.
"It's at the root of their differences. Both Morocco's and Algeria's nationhood is built around the Western Sahara issue. It goes deep in the DNA of both sides."
"The only reason to hope that there will be a breakthrough on Western Sahara is if the Algerians or the Moroccans are forced to negotiate from a position of weakness, for example if there were a coup in either country," Lawrence argued.
But as he and Mohsen-Finan point out, international consensus on the issue is finally shifting, with an ever greater emphasis on Morocco needing to improve its human rights record.
Prior to the renewal of the UN peacekeeping force's mandate in April, the United States drafted an unprecedented proposal, aggressively opposed by Morocco and finally dropped, which called for the UN mission to be tasked with human rights monitoring.
"The context of the Arab Spring has weakened Morocco on the issue of the Western Sahara, because of the question of human rights, which has become crucial today," said Mohsen-Finan.
In Rabat and Algiers, however, there are no signs that either side will change its position any time soon on an issue that has come to define their relationship, even if a new leadership emerges in Algeria.