The assembly government is being urged to save Britain's only centre for traumatised ex-service personnel in Llandudno.
The owners of the Ty Gwyn home want to turn the building into flats.
The Ty Gwyn home is the only one of its kind treating post traumatic stress disorder, and is threatened with closure next week.
The owners are trying to get planning application to turn it into flats.
A spokesperson for the assembly has said that treatment and support for veterans is available through the NHS.
Gareth Glover, a Gulf War veteran who receives treatment at Ty Gwyn, told BBC Wales he relied on the unit.
"There's always somebody here - there's a trained nurse and a care worker here 24 hours a day," he said.
"I feel devastated, really devastated. I don't know what I'm going to do when this place closes.
"Everybody is upset. It's like a lifeline. It's like a last chance saloon for a lot of us guys.
The home is the only one of its kind in Britain to treat PTSD.
"Not only has it saved my life it's keeping me alive."
Dr Dafydd Alun Jones, a consultant psychiatrist who runs clinics at Ty Gwyn, said it was vital that the centre be kept open.
"These are men who have tried to find treatment and cannot engage in the ordinary service of the NHS," he said.
"That is why Ty Gwyn was set up - as a response to a need.
"Over the years it's become an iconic place for ex-servicemen across the whole of Britain.
"It's a great despair that this service will die."
He said the assembly government needed to change the funding system to allow the unit to stay open.
"The issue is whether the funding is to be decided by innumerable local health boards across Britain, or whether we are regarded as providing a special service for a special group which are then funded centrally by core funding."
Meeting the needs of veterans
A spokesperson for the assembly government said that it was committed to supporting the health needs of veterans in Wales:
"Treatment and support is available through the NHS and a number of independent providers.
"It is for health commissioners, usually local health boards, to determine how best to meet the needs of veterans in their area and consider the most appropriate providers to offer that support, ensuring they are content with the quality of provision from all providers.
"A number of welfare services are currently being provided to veterans in Wales by an organisation called Combat Stress. This is a well respected national charity that works closely with the Ministry of Defence and with veterans themselves."