The decision to set the date for the elections came after a marathon meeting of the interim's government's Cabinet that ended Thursday night, Nepalnews.com reported.
The newly elected constituent assembly would be charged with completing a draft constitution for Nepal, a task that has remained unfinished for years, despite several deadline extensions, because of squabbling among more than 20 political parties in the strategically located country between India and China.
U.S. State Department spokeswoman Jen Psaki said Washington had been encouraging the Nepalese government to take "this important step" since the dissolution of the previous constituent assembly more than a year ago.
"We congratulate the people of Nepal as they prepare for free, fair, and inclusive elections, which are the hallmark of every democracy," Psaki said in her media briefing carried on the State Department web site. "The United States remains committed to supporting Nepal's election preparations ... ."
Nepal had been a Hindu monarchy for more than 200 years before a decade-long Maoist-led rebellion, in which thousands of people died, ended in 2006 after the Maoists agreed to a peace process.
In elections in 2008, the Maoists won the largest number of seats in the Assembly but didn't have a majority, leading to an impasse among the political parties and leaving the country without a draft constitution for electing a Parliament.