Prachanda said the split was a major reason behind the UCPN-Maoist's defeat in the November 19 Constituent Assembly election.
Speaking at a function yesterday to mark the 19th anniversary of the armed Maoist insurgency during 1996-2006, Prachanda said the parties should unify without further delay.
He said his party is in talks with the Mohan Vaidya-led CPN-Maoist. The UCPN-Maoist split in June 2012 following a series of ideological disputes with Vaidya, one of the party's senior leaders, who later formed the CPN-Maoist.
The Nepali Congress secured 196 seats while the CPN-UML won 175 seats, followed by UCPN-Maoist with 80 seats in the 601-member Constituent Assembly.
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Earlier, the UCPN-Maoist had blamed irregularities in the polls for its defeat. The Maoists, now relegated to the third position, had emerged the single largest party in the assembly after the first post-civil war election in 2008.
The UCPN-Maoist is in favour of drafting a new Constitution within a year, while the CPN-Maoist, which boycotted the November 19 election, is demanding a round-table conference to replace the current Constituent Assembly.
CPN-Maoist Chairman Vaidya argued that the UCPN-Maoist had given a blow to the cause of the people by abandoning the agenda of the "People's War".
"Prachanda and Baburam Bhattarai are making alliances with regressive forces," Vaidya alleged.