The Ministry of Defence must commit to the future of Suffolk airbase RAF Mildenhall or risk damaging the local economy, council leaders say.
The United States Air Force (USAF) announced a year ago that it would vacate the base by 2020.
A decision on its future is due in the spring, but council leaders fear the site will be “mothballed”.
They calculated that RAF Mildenhall and nearby RAF Lakenheath are worth up to £700m a year to the local economy.
Proposed changes at the bases would see the loss of 2,900 local jobs, including USAF personnel, they said.
In November it was announced that 350 personnel would be relocated from RAF Lakenheath to an airbase in Italy.
Forest Heath District Council is one of several authorities that have joined together to campaign to secure the future of the bases.
Its leader James Waters said: “We are pushing the Ministry of Defence to make a decision regarding any future military use for all or part of the RAF Mildenhall site.
“We want a commitment that the site will not be mothballed when the USAF leave – the potential damage of doing so is clear for all to see.”
The Ministry of Defence said it was reviewing future uses of the site.
“We will continue to work with the relevant councils to ensure any decision takes into account local strategic planning issues,” a spokeswoman said.