Elections had originally been earmarked for this week but legal problems and the failure of the country's main political parties to agree on how and when it should take place had led to the plan being dropped.
"The government today decided to conduct Constituent Assembly elections between mid-April and mid-May 2013. We will fix the exact date after consultation with the parties," information minister Rajkishore Yadav told AFP.
Nepal has been run by a caretaker Maoist government since the collapse in May of an interim assembly that had failed in its main task of drawing up a new constitution following a 10-year civil war that ended in 2006.
Maoist Prime Minister Baburam Bhattarai had called for November polls, but the country's election commission insisted the lack of a workable constitution meant there were no legal provisions for holding a vote.
"The government wanted to conduct elections in November 22 but it was not possible because of the special circumstance," said Yadav.
"It requires political consensus to conduct elections, hence the government will now start serious dialogue with parties and fix a date for the polls."
An estimated 16,000 people died in the 1996-2006 "people's war" fought by the Maoists against the state before the rebels turned to politics and swept to power in elections two years later.
Political in-fighting, which included a split in the ruling Maoist party earlier this year, has confounded efforts to implement a post-conflict peace plan.