- Opposition June 5 Movement says President Keita poses a risk 'to the very existence of Mali as a nation, republic and democracy'.
- After several anti-Keita protests last month, the latest rally on July 10 turned violent and deepened the political impasse.
- The June 5 Movement demands that Keita resigns for perceived failures in tackling the dire economy and Mali's eight-year conflict.
Mali's opposition alliance has rejected a plan proposed by international mediators to defuse tensions, sticking to its demand that President Ibrahim Boubacar Keita must resign.
The rejection was the latest setback in efforts to end Mali's political standoff that has spiralled into violent clashes which have left 11 people dead.
In a statement late on Friday after several meetings with a delegation from the 15-nation ECOWAS bloc, the June 5 Movement said the president's departure had been a "red line" for the mediators.
It said this ignored the risk Keita "poses to the very existence of Mali as a nation, republic and democracy".
The June 5 Movement has triggered a showdown with the government over its unflinching demands that Keita resigns for perceived failures in tackling the dire economy and Mali's eight-year conflict.
After several anti-Keita protests last month, the latest rally on July 10 turned violent and deepened the political impasse.
Three days of clashes between protesters and security forces left 11 dead and 158 injured, according to an official tally - in the bloodiest bout of political unrest in years.
The ECOWAS mediation team led by former Nigerian President Goodluck Jonathan has been in Mali since Wednesday, meeting the parties in a bid to defuse the crisis.
On the agenda were discussions about the March-April parliamentary election, the disputed outcome of which many analysts say is the root of the crisis.
Mali's constitutional court in April tossed out about 30 results from the elections in a decision that handed seats to members of Keita's party, triggering protests.
But the mediators' compromise offer is substantially similar to an earlier offer made by Keita, which the opposition has already rejected.
The mediating team proposed that Keita remains president, for example, but that new judges be appointed to the constitutional court so that it could revisit its decision on the parliamentary election.
A "new government of national unity" should also be formed, mediators said.
Jonathan, from the ECOWAS team, told reporters on Saturday negotiations had not failed and that meetings would continue.
He added that the ECOWAS team would issue a statement on Saturday or Sunday.
Reporting from Dhaka, Senegal, Al Jazeera's Nicolas Haque said regional leaders were eager to end the political crisis in Mali amid fears of the unrest spreading.
"There is a real fear that these protests in Bamako could spread to other capitals in the region ... where we have seen high levels of distrust among citizens of their leadership," he said.
"There is going to be a presidential election in neighbouring Burkina Faso and also an election in Ivory Coast, so they are closely watching this."
One of the June 5 Movement's leaders, Choguel Maiga, said late on Friday the mediators' proposals had "reduced our entire struggle to electoral issues".
In the statement issued on Friday, the opposition movement said it was insisting the president quit based on his "proven inability to turn Mali around" and the loss of territory, among other issues.
Swaths of Mali lie outside of government control because of an armed conflict that began in the north in 2012, before spreading to the centre, as well as into Burkina Faso and Niger.
The conflict has claimed thousands of lives and driven hundreds of thousands from their homes.
With the latest political crisis, Mali's allies and neighbours are eager to avoid the fragile Sahel nation of some 20 million people sliding into chaos.