Morocco's steadfast opposition to US-backed plans to broaden the mandate of UN peacekeepers in the disputed Western Sahara to human rights monitoring threatens to sour relations with key ally Washington.
Rabat on Monday described the proposal as an attempt to "deform" the mandate of the two-decade-old peacekeeping force, and has launched a frantic lobbying campaign in defence of the kingdom's "sovereignty" over the territory it annexed in 1975 in a move never recognised by the international community.
Government supporters have called a protest march to the US embassy on Sunday, after a shrill campaign in the pro-government press all week.
The UN peacekeeping force has monitored a ceasefire in the Western Sahara between Morocco and the pro-independence Polisario Front since 1991, but unlike similar missions elsewhere, it is not charged with monitoring human rights.
When its mandate comes up for renewal at the Security Council at the end of April, UN sources say Washington has drafted a resolution that will propose adding "monitoring and reporting on human rights" to its responsibilities.
The US embassy admitted on Friday that there had been some negative fallout on relations but played down its extent.
"Certainly this is a bump in the road. But I think Morocco will remain a strong ally and a partner," embassy spokesman Rodney Ford told AFP.
In the clearest sign yet of its displeasure, Morocco cancelled annual war games with the US military, which had been due to take place throughout April and involve 1,400 US and 900 Moroccan military personnel.
The foreign ministry on Friday denied that any major rights abuses took place in the Western Sahara, said the initiative to broaden the UN force's mandate threatened the peace process, and labelled the Polisario Front a "terrorist organisation."
"This approach creates a false symmetry between a sovereign state, which respects its international obligations and a terrorist organisation," said deputy foreign minister Youssef Amrani, adding that mechanisms already existed to monitor human rights in what he called the "Moroccan Sahara."
Earlier in the week, government spokesman Mustapha Khalfi summoned the foreign press to underline Morocco's categorical rejection of the US plan.
Giving the UN mission a rights monitoring role is something human right groups and the Polisario Front have been advocating for years in the face of repeated allegations of torture of independence activists by Moroccan forces.
Earlier this month, UN chief Ban Ki-Moon added his voice to the calls, pointing to an "ever more pressing" need for "comprehensive and sustained" human rights monitoring in both the Western Sahara and Polisario-run refugee camps in neighbouring Algeria.
The 1991 ceasefire left Moroccan troops in control of all the Western Sahara's main population centres with Polisario forces restricted to a strip of desert on the Algerian border.
But efforts to broker a lasting settlement have been deadlocked by Morocco's refusal to agree to the Polisario's demand for Sahrawis to decide whether or not they want independence in a UN-monitored referendum.
The impasse has stoked growing international concern amid insecurity this year in other parts of the Sahel, notably Mali where French-led troops have been fighting an Islamist insurgency.
The International Crisis Group's North Africa director, Bill Lawrence, said it was unlikely the spat would have a lasting impact on historically close ties between Washington and Rabat, despite Morocco being "very upset."
"The strategic relationship will probably trump this kerfuffle. But some things have changed. Certainly human rights is growing in importance, both domestically in Morocco and internationally," he said.