Bolivian President Evo Morales has suffered a major setback in his plans to give the country a new constitution to favour the indigenous majority.
The president's constitution plans have split the country
The National Electoral Court has postponed a referendum on a new draft constitution planned for 4 May, saying there is not enough time to prepare.
Mr Morales has faced sustained opposition to his plans from the resource-rich east of the country.
But the court also suspended plans to consult on greater autonomy there.
MPs from Mr Morales' Movement Towards Socialism (Mas) party approved plans to hold the May referendum at the end of last month.
There was little participation by opposition politicians, some of whom were prevented from entering Congress by government supporters outside.
But now the head of the National Electoral Court, Jose Luis Exeni, says the vote cannot go ahead.
"No technical, operative, legal or political conditions exist to allow it to go forward," he said.
He added that the referendum failed to meet a constitutional requirement that it be held at least 90 days after being approved by Congress.
The draft constitution was approved last year by a constitutional assembly which has been boycotted by opposition groups.
The president cannot afford to let down his supporters, say analysts
It would grant greater powers, and a bigger share of Bolivia's land and resources, to the country's indigenous groups - who make up the majority of the population but have long been marginalised by the country's European-descended elite.
But opponents in four eastern states - also home to a large part of Bolivia's oil and gas deposits - say it would unfairly privilege indigenous groups over the rest of the population.
They also suffered a setback on Friday, as the court delayed their own referendums on proposals to declare greater autonomy.
Both referendums were potentially divisive, reports the BBC's Latin America correspondent, Daniel Schweimler.
But President Morales came to power promising great change in Bolivia, the poorest country in South America, and one way or another, he must push his proposals through, our correspondent says.
However, every time he does, the splits in Bolivian society widen a little more, he adds.