Presidential elections in Bolivia have been put on hold after a court ordered the redistribution of several seats in the country's parliament.
The court ruling could affect the level of support for Evo Morales
Three highland provinces will lose representation, while the eastern area of Santa Cruz will gain more seats.
The head of Bolivia's election board said the vote, due before the end of the year, could not take place until the court ruling was implemented.
The affected provinces branded the decision a conspiracy.
Protesters there have threatened blockades on major roads.
Bolivia's last elected President, Carlos Mesa, quit in June after mass demonstrations against his government and weeks of blockades brought the country to a standstill.
Interim President Eduardo Rodriguez agreed to hand over power to a democratically elected leader before the end of the year.
Mr Rodriguez called for calm and said that Congress would have to find a political solution to the issue.
Oscar Hassenteuffel, the head of Bolivia's election board, said no vote could take place until parliament approved the changes.
Bolivia's constitutional court ruled against an electoral law because it did not use population information from the 2001 census as the basis for parliamentary elections.
The court said that Potosi, Oruro y La Paz provinces should lose seats, while Santa Cruz would gain at least four.
If approved, the changes are likely to affect the campaign of indigenous leader Evo Morales, who enjoys strong support in the highlands but is less popular in the east.