An overtime ban is already in force.
The Transport Workers' Union AKT and port operators failed to reach an agreement on Tuesday.
The two sides were to have met at 1 pm on Wednesday but state labour mediator Esa Lonka said the meeting would be pushed back. That is because he and AKT chair Timo Räty were both busy trying to resolve the road transport strike. That dispute ended late Wednesday afternoon.
The strike would bring the country's ports to a standstill. It would also curb foreign trade by about 80 percent.
The strike was initially scheduled to begin on February 19. However, it was delayed until March under the direction of Labour Minister Anni Sinnemäki.