Workers have voted to take strike action at the UK's busiest container port in a dispute over outsourcing.
The union Unite claimed the Port of Felixstowe is transferring engineering jobs to cut costs, and fear it is "the thin end of the wedge".
One worker said an industrial dispute would be "catastrophic", given local economic reliance on the Suffolk port.
The Port of Felixstowe has been approached for comment.
The 116 engineers voted 98% to take strike action over a plan to transfer members of the tyre-fitting operation to another company.
'Affect more engineers'
Unite claims to have 1,900 members among the port's approximately 3,000 workers, though only the engineers will take the strike action.
The Port of Felixstowe is the UK's biggest container port and in 2018 handled 37% of the country's cargo arriving by container.
It also loads 40 rail services a week and a terminal which loads and unloads two daily ferries for lorries.
Unite regional officer Miles Hubbard said: "At present, the threat is just to the tyre-fitting operation, but we fear that this could affect most of our engineering members going forward."
Port management would be told strike dates in the coming days, he said.
The union would ballot its 1,800 remaining members over strike action if the port's "outsourcing agenda continues to gather momentum", he added.
One worker, speaking to the BBC anonymously, said: "An industrial dispute could be catastrophic for the local community, [as] Felixstowe and the surrounding areas all rely on the operations at the port."
The employee said he feared any disruption could lead to shipping contracts being transferred to other ports "and then not coming back".