Both the union and employers groups have rejected a resolution proposal in a cleaners' dispute on Wednesday, triggering a strike that could see nearly 30,000 people walk out.
The strike targets workers at 18 companies and is set to begin at midnight. It will last for three days, if no solution is found.
The PAM service sector trade union and real estate industry employers have been in dispute over a new collective agreement since January. The previous agreement ended in February.
PAM has previously said that the proposed pay rises in the dispute were not enough to offset increased living costs as inflation rises.
Those proposed raises were in line with percentages seen across the Finnish economy, at roughly six percent over two years. However, cleaners' representatives said their sector is so low-paid that euro-denominated pay rises were necessary, as the percentages were too small.
There have already been two strikes in the sector this year, but the one starting on Thursday is the largest yet.
PAM also issued strike warnings for two further walkouts, one two-day action on 13-14 April and one targeting seven of the largest companies in the sector, beginning on 15 April and continuing until further notice.
Most workers in Finland are covered by a collective agreement in their sector. This contract governs pay and conditions of work, with wage rises agreed between unions and employers, and applied to every worker in the sector whether or not they are a union member.
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