Under a peace treaty signed last year between armed resistance groups and the government, a Constituent Assembly is to be elected to rewrite the constitution and decide a new political system for Nepal, currently a constitutional monarchy.
King Gyanendra, Nepal's monarch, has been stripped of most of his powers after being forced to end a much-criticised 14-month period of authoritarian rule last April.
Nepal's Maoists, which have fought against the monarchy, want the interim government to declare a republic prior to the polls.
Leaders of the eight ruling parties had initially set June 20 for the polls, but postponed the date after election officials sought more time to make technical preparations and for the government to pass new election laws.
Officials have also said the security situation in southern Nepal needs to be improved before any elections can take place.
Violent protests and strikes in the south of the country since January have stopped officials from registering voters.