The leaders of the four main political parties reached the agreement late on Monday, said Narayan Kaji Shrestha of the Unified Communist Party of Nepal Maoist.
The agreement is expected to be formally signed at a meeting later on Tuesday where they also would finalize the election date and the makeup of the new council of ministers.
The parties want Supreme Court chief justice Khilraj Regmi to be the chairman of the council. The idea of appointing the chief judge as the head of the interim government to conduct elections was proposed by the ruling Maoist party last week because these parties could not agree on who would lead the new interim government.
Nepal has been without a fully functioning government and parliament since last May. Prime Minister Baburam Bhattarai has been running a caretaker government. Bhattarai's government has been unable to hold elections, with opposition parties wanting Bhattarai's removal before a vote is held.
The Constituent Assembly was elected in 2008 with the task of writing a new constitution after Nepal's centuries-old monarchy was abolished and the country was declared a republic. The assembly failed to complete the task even after the term was renewed and finally ended in May 2012.
It was not clear how the head of the judiciary would also be given the task of executive head but the leaders said they would seek to amend the interim constitution.