Large parts of Bordon Whitehill are used for training by the MoD
Plans announced last week for a new "eco-town" in east Hampshire are already facing a potential problem.
The government confirmed that one of four new "carbon neutral" towns would be built at Whitehill Bordon.
East Hampshire District Council said the scheme would create up to 5,500 new homes and 7,000 new jobs for the town.
But a large part of the eco-town is dependant on the Army moving out of its training sites in the area, a plan that has not yet been finalised.
If the Ministry of Defence (MoD) moves out it would free up 250 hectares of land on which the new town would be built.
But that depends on the government signing a contract, which would be privately financed, for a major shake-up of defence training.
The MoD said in a statement that it was committed to the plan and that final contracts were scheduled to be signed next year.
"However, until final contracts are signed it would not be sensible to make the site available to become an eco-town," the statement said.
MoD training would not move until after 2014.
But leader of the council Ferris Cowper said: "Both these projects are long-term.
"So really if you waited for one to be firmed, you'd be far too late to start the other one.
"So we've got them both going now so that when they come together, as we confidently expect they will do, then we will have the most wonderful marriage of two superb projects."
Opponents of the scheme believe that the council is misrepresenting the views of local people, who, they say, do not support the plan.
Mr Cowper said the council would communicate with all residents "house by house, door by door" later this year.
A draft master plan for the town is currently being developed and further consultations will be held before it is adopted.