In the past, Maoists have said they have 35,000 fighters but have not provided details of their arms.
Last month, James Moriarty, the US ambassador, claimed the former rebels were buying inferior arms in neighbouring India to store in UN containers and were retaining their modern weapons, an assertion the Maoists and the government reject.
The Maoists and multi-party government mandated the UN to monitor Maoist fighters and their arms as part of the November peace deal that put an end to the anti-monarchy Maoist revolt that started in 1996 and claimed more than 13,000 lives.
|Maoist members have taken 83 seats in the|
newly formed Interim parliament [EPA]
Maoist arms have been catalogued, bar-coded by registration teams and stored on racks inside metal containers. Maoists will keep the keys but UN teams will provide a 24-hour watch.
The landmark peace deal has seen the Maoists take 83 seats in the 329-member provisional parliament and they are also set to join an interim administration.
Dwyer said the second stage of arms monitoring, which includes verification of information about the age and number of years combatants had served in the Maoist force, would start soon.
Human-rights group accuse the Maoists of recruiting children in their ranks, which the former rebels deny.
In the final phase of disarmament, the Nepal Army will also store an equal number of arms ahead of this year's elections for a constituent assembly that will draw up a new constitution and decide the fate of the monarchy - which the Maoists want abolished.