The Fire Brigades Union is claiming job cuts will be made in Coventry and Birmingham.
It says 18 posts will be made redundant in Coventry, with two traditional fire engines being taken off the road and replaced by one smaller vehicle.
A further 16 firefighters will lose their jobs at stations in Birmingham, with another two fire engines decommissioned, also to be replaced with smaller fire vehicles.
A statement from West Midlands Fire Service is expected at some time this morning.
More top news
Leah Washington, 17, had to have her left leg amputated after being trapped for hours on The Smiler rollercoaster at the theme park.
Fine and dry this evening and overnight with showers on Sunday afternoon.
Warm sunny spells through the evening, followed by dry conditions throughout the night.