The new threat on Wednesday came after Sudan's military leaders ignored an earlier deadline to step aside within a 15-day period set by the bloc on April 15. 

The AU's Peace and Security Council said it noted the military's failure to transfer power to a civilian authority "with deep regret", but said it was giving the council "an additional period of up to 60 days" to do so. 

The bloc also reiterated "its conviction that a military-led transition in the Sudan will be totally unacceptable and contrary to the will and legitimate aspirations, to democratic institutions and processes, as well as respect for human rights and freedoms of the Sudanese people".

The military assumed power in Sudan after toppling the country's long-time ruler Omar al-Bashir following months of anti-government protests.

It promised to hold elections within two years but protesters have rejected that and remained on the streets of the capital, Khartoum, demanding immediate civilian rule. 

The council, led by General Abdul Fattah al-Burhan, has been negotiating with protest leaders on the formation of a new transitional government. But the two sides are divided over the role of the military, which is dominated by al-Bashir appointees. 

The Sudanese Professionals Association (SPA) and its allies, which organised the four months of demonstrations that drove al-Bashir from power on April 11, have accused the generals of clinging to power.

The group has called for mass rallies on Thursday and threatened a general strike. The military, meanwhile, has warned against any further "chaos" and demanded that protesters clear roadblocks around their sit-in outside the military's headquarters in Khartoum.

'Orderly transition'

Meanwhile, a top United Arab Emirates official said Arab states support an "orderly" transition in Sudan that balances the ambitions of the people with stability.

"Totally legitimate for Arab states to support an orderly and stable transition in Sudan. One that carefully calibrates popular aspirations with institutional stability," UAE Minister of State for Foreign Affairs Anwar Gargash said on Twitter

"We have experienced all-out chaos in the region and, sensibly, don't need more of it," he added.

The UAE and Saudi Arabia last month pledged three billion dollars in aid to Sudan, throwing a lifeline to the country's new military leaders as they seek to consolidate relations and prevent any repetition of the chaos of the Arab Spring uprisings of 2011.

Sudan is heavily dependent on the financial support of its Gulf Arab allies and one of the first actions of the military council was to promise no change in Khartoum's commitment to the Saudi-led coalition's intervention in Yemen, where its forces are fighting Iranian-backed Houthi rebels to restore the government of President Abd-Rabbu Hadi Mansour. 

With the loss of most of its oil production to newly independent South Sudan in 2011, Sudan lost more than half of its foreign exchange earnings leading to a chronic shortage of hard currency that has led to spiralling inflation and frequent shortages of imported commodities.

A tripling by the government of the price of bread in the face of a chronic shortage of flour was the immediate trigger for the four-month nationwide protests that led to al-Bashir's overthrow.

Central bank deposits by the UAE and Saudi Arabia have so far staved off any further slide in the value of the Sudanese pound, while cheap credit for imports of basic goods has averted more widespread shortages.