"Those involved on both sides are to be congratulated for their hard work in finalising an agreement which is entirely a Nepali achievement," said Ian Martin, the personal representative of UN chief Kofi Annan in Nepal.
The deal paves the way for the rebels to enter mainstream politics, after they declared an end to their decade-long "people's war" and agreed to place their army and weapons under UN supervision.
"I hope that we will quickly be able to reach tripartite agreement on the full modalities for the management of arms and armies," Martin said.
Annan is keen to move as quickly as possible to offer assistance in the peace process, Martin said.
"The Secretary-General has said that he intends to move promptly to respond to the request to the United Nations to help in key areas of the peace process," Martin said in the statement.
The deal on Tuesday ends the conflict that has killed at least 12,500 people since 1996, when the rebels launched their "people's war" aimed at toppling the monarchy and installing a communist republic in the tiny country sandwiched between India and China.
Prime Minister Girija Prasad Koirala and Maoist rebel leader Prachanda signed the deal seven months after King Gyanendra abandoned absolute rule following violent street protests.

Copyright AFP (Agence France-Presse), 2006