Bolivia's top electoral authority on Friday indefinitely postponed a May 4 referendum on a new constitution intended to give more political power to the nation's long-oppressed indigenous groups.

Citing logistical concerns, the National Electoral Court ruled that it would be impossible to ensure the "legal guarantees, sufficient time and adequate electoral environment" on such short notice for the referendum, which is backed by President Evo Morales.

It also suspended referendums planned in four opposition-controlled eastern states on proposals to declare greater autonomy.

"The National Electoral Court's decision is fair as long as the state electoral courts" also abide by it, said Cesar Navarro, a legislator from Morales' Movement Toward Socialism party. "But it's not fair if the decision only puts the brakes on the national referendum."