The deputy chief of Nepal's Maoist rebels says peace talks with the government could break down if it insisted on retaining monarchy.
Mr Bhattarai is the number two Maoist leader
Baburam Bhattarai said Nepalese people favoured abolishing the monarchy.
The rebels have extended a ceasefire but urged the government to advance talks. Mr Bhattarai said they would continue their "fight" if talks failed.
The rebels called a truce after King Gyanendra ended direct rule and restored parliament in April.
The Maoists and a seven-party alliance clinched a landmark power-sharing deal in June.
The government and rebels have differed recently over a government plan for the United Nations to be involved in the decommissioning of the rebels' weapons.
The two sides have also differed on the future of monarchy in the country.
The number two in the Maoist communist party told a meeting of businessmen in the capital, Kathmandu, that the peace talks with the government were stalled.
"The talks are very close to collapse. The dialogue process is stuck at a very sensitive stage," Mr Bhattarai was quoted as saying by the Reuters news agency.
He said his party would not return to the jungle and would launch a peaceful movement in order to make the country a democratic republic.
Mr Bhattarai accused the government of "dragging its feet" away from "all the agreements reached between us and also trying to protect the king".
The rebel leader also accused Prime Minister Girija Prasad Koirala of trying to protect King Gyanendra, who gave up direct power in April following weeks of pro-democracy demonstrations.
He said that if it was trying to protect the monarchy, the Maoists would launch a new struggle; but this would, he stressed, remain peaceful.
The BBC's Charles Haviland in Kathmandu says that talks between the government and the rebel party are deadlocked, mainly over whether or not the Maoists should be fully disarmed before joining an interim government.
Our correspondent says that some analysts believe Dr Bhattarai, known for his hardline rhetoric, may be trying to shift attention away from the weapons issue to the question of the monarchy.
Mr Koirala has been advocating a ceremonial role for the monarchy since it was stripped of its powers and privileges in May.
"We want to caution and warn him [Mr Koirala] that we will be compelled to leave if the government continues to protect the monarchy," Mr Bhattarai said.
The rebels have differed with the government over giving up arms
He said his party was not ready to lay down arms unless the outcome of the Constituent Assembly elections became public.
The political landscape has been shaken-up since the king restored representative rule.
Opposition parties have since joined the government.
The new government has released rebels from jail, dropped terrorism charges against them and agreed to the ceasefire.
But differences remain between the two sides, particularly over the future of the monarchy.
The rebels hope elections will clear the way towards abolition of the monarchy.
More than 13,000 people have died in violence in Nepal since the rebels began their fight for a republic 10 years ago.
During the insurgency, there have been two other sets of peace talks, three years ago and five years ago.