Saturday, Prachanda had offered to give up leadership to an independent prime minister and announced that the convention would come up with a formula to end the political stalemate.
"We know that the constitution doesn't have a provision whereby a chief judge can lead such a government. But we are sure that the opposition parties will agree on this," Sapkota said.
"If this doesn't work, there's no other option. This is the last option. The opposition parties should come up with a better alternative. If there's none, we will launch a nationwide movement to sensitise people about the issue.
The Maoists joined hands with other political forces in 2005 after signing a 12-point deal to topple the monarchy and establish multi-party democracy after the decade-long civil war in which more than 16,000 died.
The Maoists joined mainstream politics at the end of the civil war in 2006 and won the 2008 Constituent Assembly polls that ended the 240-year-old monarchy.
Nepal's transition to democracy has been beset by the ethnic, caste, religious and ideological differences that have made agreement among the country's powerbrokers impossible.
The Maoists want the creation of up to 14 states named after ethnic groups, but their rivals refuted the plan saying it would fuel unrest.