Tension rose in Bolivia's election crisis on Sunday after an opposition figure called on the military to take ‘the side of the people’ and vowed to oust leftist President Evo Morales.
Deadly unrest has gripped the country since Morales was named winner of the October 20 election.
The president's opponents have branded the result a fraud. Some protesters are rejecting both candidates and demanding fresh elections.
Late on Saturday, Luis Fernando Camacho, a conservative opposition leader in the eastern Santa Cruz region, issued an ultimatum to Morales.
‘He has 48 hours to step down, because at 7:00 pm (2300 GMT) on Monday, we are going to take decisive action right here and we are going to make sure that he goes,’ Camacho told a gathering of supporters.
He called on the military to ‘be on the side of the people.’
Camacho did not specify what kind of action he had in mind. His supporters have previously taken over public buildings.
The military has so far stayed neutral in the electoral dispute but calling on the military is a delicate move in Bolivia.
The country saw numerous military uprisings dictatorships before civilian rule was established in 1982.
Morales is looking to remain in power until 2025 with a fourth term.
His election win was ratified by the Supreme Electoral Tribunal -- but only after an abrupt and unexplained shift in the vote count in his favour.
The Organisation of American States is carrying out an audit of the vote.
The country's constitution limits a president to two successive terms. But Bolivia's constitutional court authorised Morales to stand for a fourth mandate.
The court, like the election tribunal, is made up of members appointed by Morales's Movement for Socialism.
The interior minister last week said two demonstrators were killed in clashes between supporters of the rivals. State authorities say 140 people have been hurt in the unrest.