The process to award a £3bn deal for new military vehicles has been called "clandestine" by a Welsh MP.
Caerphilly MP Wayne David is concerned a German firm will get the contract to replace Scimitar armoured cars.
He called for a "fair and open process" with General Dynamics UK plants in south Wales allowed to bid.
The Ministry of Defence has said announcements would be made by the end of the financial year, which is next Thursday.
Reports suggest that the Boxer, which is manufactured by Munich-based ARTEC, could be the chosen supplier.
In January, Wales' Economy Secretary Ken Skates urged the UK's Defence Procurement Minister Guto Bebb to consider the Piranha vehicle made by General Dynamics UK, which he said could supply suitable vehicles more cheaply and save Welsh jobs.
Mr David, Labour's shadow minister for defence procurement, told the BBC that the American-owned firm - which has plants at Oakdale, in Caerphilly county, and at Merthyr Tydfil - was keen to bid.
"There should be a fair and open process," he said.
"Every company should have a chance to bid for a contract of this size."
The issue had been raised by Conservative MP Dr Julian Lewis during Business Questions in the Commons on Thursday.
He asked for assurances that the decision would be announced in the Commons when Parliament is sitting and not during the Easter recess.
Leader of the House Andrea Leadsom said that it was an important point, but she could not answer the question at the moment.
The Ministry of Defence pointed to a previous comment by Mr Bebb that announcements on the mechanised infantry vehicle programme would be made before the end of the financial year, which falls on Thursday, 5 April.