The website Inner City Press, which follows UN affairs, published the report which it said had been leaked.
It was apparently written by a special team assigned by Secretary General Ban Ki-moon to draw up recommendations for the UN's new role in Libya.
However, the UN has not confirmed its authenticity.
The report appears to be an internal planning document that could serve as the basis for a new UN mandate in Libya.
It suggests a UN mission with a core staff of 61 civilians, for an initial three month period, to help Libyan rebels organise a peaceful transition to democracy.
'Nato presence'Beyond that, it recommends the deployment of up to 200 unarmed military observers - principally to monitor the process of dealing with forces loyal to fugitive leader Col Muammar Gaddafi - as well as up to 190 UN police officers to help train local forces.
All of this would be implemented only if requested by the Libyan transitional authorities and approved by the UN Security Council.
The document says it would be beyond the UN's capacity to deal with any major destabilisation in Tripoli.
In such a case, it says, Nato would continue to play a role because its UN mandate to protect civilians does not end with the collapse of the Gaddafi regime.
The report also details how the UN could support the establishment of an inclusive and legitimate interim government, and help it prepare for the election of a provisional national congress to draft a constitution in the next six to nine months.