Bolivia's general election - supposed to be taking place on 4 December - has been postponed amid a row over the reallocation of congressional seats.
Evo Morales criticised the decision to delay the vote
The election was called earlier this year as a way of ending street protests that had led to the resignation of President Carlos Mesa in June.
But a fresh row has broken out after a court awarded more seats to the more developed eastern part of Bolivia.
The vote can still be held in December if the politicians reach a deal soon.
The election board said it was up to interim President Eduardo Rodriguez to get the quarrelling politicians to agree.
Mr Rodriguez has said he will step down in January even if an election has not been held - leaving the possibility of a power vacuum.
The left-wing leader, Evo Morales, has accused the country's traditional parties of using the dispute to stop him becoming president.
BBC Americas editor Simon Watts says there is a real possibility that this latest dispute could cause street protests once again.
The interim government had hoped that voting would help ease divisions over how to develop the energy industry, and how much autonomy Bolivia's diverse provinces should enjoy.
But last month the constitutional court ruled that fast-growing areas, mainly in eastern Bolivia, deserved more election seats.
Although the decision was based on the census, it re-ignited the regional tension that was one cause of the original unrest.
Congress has held weeks of debates about how to implement the ruling, but missed the deadline amid boycotts by some deputies and threats of strikes in some provinces.
Mr Morales, ahead in the opinion polls, hopes to become Bolivia's first indigenous president. He has pledged to improve the rights of the indigenous majority and to lift restrictions on coca production.
His closest election rival is the US-educated engineer Jorge Quiroga.
Mr Quiroga, who served as president in 2001-02 after President Hugo Banzer fell ill, has pledged to work to get Bolivia's foreign debt cancelled.
The Andean country - the poorest country in South America - has Latin America's second largest gas reserves, and hydrocarbons are its main source of income.