Preparations are being made for it to be blown up in a controlled explosion tomorrow morning.
A spokesperson for the Whitehill & Bordon Regeneration Company said: "The device has been sitting buried for around 75 years and requires the services of a specialist disposal unit.
"A 200-metre exclusion zone is currently in force and this will be extended to 1,500 metres at the time of the disposal.
"There will be a need to clear everyone from all homes, buildings and roads within this zone.
"We urge the public not to break the exclusion zone and to avoid the area completely wherever possible.
"Plans are being put in place to provide alternative accommodation to anyone unable to return to their homes overnight."
Experts estimate the exclusion zone could be in place for "up to 30 hours", taking the restrictions beyond midday tomorrow and cancelling the inclosure parkrun.
The spokesperson said: "We appreciate the inconvenience that this may cause to local residents, but the safety and welfare of the local community has to be our number one priority."
Contractors discovered the bomb while working on the drainage areas at the Hogmoor Inclosure SANGS near Hogmoor Road.
Building sites, a caravan site and a concrete works were evacuated as a precaution and the public were asked not to visit Hogmoor Inclosure.
Closures were put in place on Hogmoor Road, Firgrove Lane and Oakhanger Road today but the A325 was not affected.
The spokesperson outlined the work being done to ensure the bomb is disposed of safely: "Our contractors have already begun the process of building sand walls and protective works surrounding the device.
"Royal Engineers will be on site overnight and will be using over 300 tons of sand to create a blast wall around the bomb in order to prepare it for a controlled explosion, likely to take place on Saturday morning.
"Ministry of Defence Police will also be on site to enforce the exclusion zone, with the help of the Hampshire Constabulary."
Despite Bordon's history as an Army town, and recent extensive excavations for the building of 1,000 new homes, this is the first unexploded bomb to be found there.
The spokesperson said: "Many former military bases across the UK have been redeveloped in recent years, and careful work is undertaken to investigate and remediate these sites prior to any work commencing.
"The discovery of unexploded bombs is a rarity, but we have protocols in place for such eventualities.
"Bordon was designated as a training and depot facility historically, making the presence of live munitions unlikely.
"While we cannot rule out incidents as we have experienced today, the risk associated with them is low."