Workers at Bridgend's Ford factory have voted in favour of strike action over concerns for the plant's future, BBC Wales understands.
A document seen by BBC Wales showed 52.1% of workers who voted were in favour of strike action, while 47.9% were against.
Ford called the ballot "premature" and said it remained committed to "ongoing constructive dialogue" with unions.
In March, unions said the plant could potentially lose 1,160 jobs.
When asked if they were in favour of action short of a strike, 71.9% of workers who voted were in favour with 28.1% against.
The American car giant announced plans last September to cut the level of investment from a planned £181m to £100m and halve the production of its new generation of petrol engines made in Bridgend.
The Unite union, which represents the majority of employees at Ford's Bridgend engine plant, said the ballot result was a "clear indication of members' feelings" and it had invited the company to meet at the earliest opportunity to "seek a resolution to this situation".