It also clears the way for the Maoists to join an interim government that will oversee the elections, and will allow them to take seats in an interim parliament.
Civil war has continued in Nepal for over 10 years in opposition to the country's 200-year-old monarchy.
The assembly will vote on the continuation of the monarchy and the Maoists have vowed to honour the outcome, even if the assembly decides to maintain a ceremonial monarchy.
C. K. Lal, a political analyst, said: "This will have a meaning only if a majority of the Maoist cadres think that they stand to benefit by it - that is the possibility of the abolition of the monarchy through peaceful means. Otherwise, they can revolt anytime."
A ceasefire has been observed for more than six months, but human rights groups have said extortion and conscription by guerilla fighters have continued.
Last week, Prachanda said he believed peace was coming to Nepal, but that armed struggle could not be ruled out until the 35,000 Maoist fighters had been merged with the state army.