Hopes are rising that south Wales could become home to a new defence training academy, creating thousands of jobs.
An artist's impression of how the military academy would look
The Ministry of Defence is expected to reveal on Wednesday whether the Metrix consortium based at RAF St Athan has won the contracts, worth up to £14bn.
Labour MPs are increasingly confident the consortium could be chosen to provide at least one of the two packages on offer.
The new training centre could create 5,000 jobs in the Vale of Glamorgan.
St Athan is competing against a rival bid from RAF Cosford in Shropshire, but Welsh MPs believe months of high-profile lobbying may be about to pay off.
It is hoped the Metrix bid will secure at least the package to provide training to all the armed forces for the next 25 years. It would be the largest single government investment Wales has seen.
Defence Secretary Des Browne will announce the preferred bidder in a statement to MPs tomorrow, a UK Government source has told the BBC.
Several Welsh Labour MPs have been invited to Downing Street afterwards, raising hopes the announcement will be good news for south Wales.
The announcement follows a review of defence training requirements.
In future, training will be provided across the armed forces, rather than to a single force.
Welsh Secretary Peter Hain has said the proposed military training academy at St Athan would be a massive boost for the whole of south Wales.