"The signing ceremony will be held at Birenrda International Convention Centre Tuesday evening," Arjun Narsingh, a delegate from the Nepali Congress Party, told AFP.
The draft agreement was struck on November 8 and had been due to be signed last week. A Tuesday deadline was then set. Under the deal, the rebels are to end their "people's war", join an interim government and place their arms and troops under UN monitoring.
The 90,000-strong Nepal Army was also supposed to be confined to quarters by Tuesday.
"It's unlikely that we will meet this deadline, because the United Nations is unlikely to deploy its personnel for verification of the People's Liberation Army weapons and personnel by Tuesday," rebel negotiator Dev Gurung explained.
He did, however, stress that "our PLA (People's Liberation Army) comrades have already gathered in the seven areas where they will be confined".
The personal representative sent by UN chief Kofi Annan said last week that the world body was waiting for the peace agreement to be signed before it could begin its monitoring mission.
Once deadly foes, the government and Maoist rebels have observed a cease-fire for more than six months, after they co-operated in April to organise mass protests that forced King Gyanendra to restore parliament and end direct rule.
The peace deal leaves the king facing an uncertain future, with the fiercely republican rebels vowing they will not rest until Nepal's almost 240-year-old monarchy is abolished.
Some of the parties in the coalition favour a ceremonial role for the king, who is revered by many as a Hindu deity.
But on Monday an official panel called for Gyanendra to be punished for ordering a deadly crackdown by security forces during April's protests.
The rebels say they are undergoing a major political makeover, but are also under pressure to put an end to activities including alleged forced recruitment.
On Monday the United States, which continues to class the Maoists as a terrorist organisation, denounced what it said was "the continued forced recruitment of Nepalese, including children".
A top rebel denied the charge.
"We have not recruited children in our People's Liberation Army, but summoned all our party cadres who had gone to their homes after the cease-fire," said Dina Nath Sharma, a rebel peace negotiator.
Nepal's civil war has claimed at least 12,500 lives since 1996.
This is the third time that the rebels and government have tried to hammer out a peace deal in the impoverished Himalayan nation. Two previous attempts in 2001 and 2003 failed, plunging the country back into conflict.

Copyright AFP (Agence France-Presse), 2006