The Ministry of Defence has confirmed a storage centre near Llanelli will close next year with the loss of 190 jobs.
The MoD has announced a major shake-up of defence sites
Workers had campaigned to keep the Defence Stores and Distribution Centre in Llangennech open since its future was first cast into doubt in 2005.
But now they have been told the centre, which stores and distributes MoD forms and publications, will shut in 2008.
It is part of a wider shake-up of Ministry of Defence sites across the UK.
Politicians and union officials, including Llanelli MP Nia Griffith, had met government ministers in a bid to keep the site open.
But workers have now been told it will close by June 2008.
Llangennech holds MOD forms and publications, as well as navy timber, metals and support stock for warships.
It also houses the MoD civilian records archive, which contains more than two million personal files, as well as VAT records on behalf of HM Customs and Excise.