Canterbury manufacturers are questioning whether Lyttelton Port workers realise the implications of their industrial action.

They are pleading with Port workers and the Port company to resolve their dispute as shipment delays continue.

Around 200 workers represented by the Rail and Maritime Union are set to strike for five days from midnight Wednesday over fair pay and safety.

They want a four percent pay increase in the first year, but the port company will only offer three.

Manufacturers' Network Chief Executive Dieter Adam says the flow-on effects of their actions are widespread.

"It's not like when there's one factory being on strike and it only affects that one factory and its customers.

"This affects a lot of the operations for the whole of the South Island."

Dieter Adam says he's heard from at least a dozen manufacturers who can't get their products either in or out of the port.

He says the uncertainty is hurting his members in the pocket and affecting relationships both here and overseas.

"We've got one container with $400,000 worth of tools, waiting to be shipped to Melbourne urgently.

"The customer on the other side of the Tasman is obviously not going to be too pleased about the delay and the uncertainty."

Dieter Adam says even if the union withdraws its strike action, the damage is already done as ships have already been diverted.