Posti workers will go on strike next Monday, National Conciliator Vuokko Piekkala announced on Thursday.
She said that the two sides' positions were so far apart that no agreement was in sight. The next official talks are scheduled for next Wednesday, 13 November.
Workers in mail delivery, handling and transportation jobs are to stay off the job from 6 am on Monday, 11 November until midnight on Sunday, 24 November.
The Finnish Post and Logistics Union (PAU) also confirmed that the walkout will go ahead. The trade union said that the conditions were not right for the mediator to present a compromise proposal.
PAU's board is to meet on Friday to finalise plans for the strike, which has been threatened since 22 October.
Management rejects claim of wage cuts
A previous job action in early September was suspended after a couple of days. That followed a promise from the cabinet minister in charge of overseeing majority-state-owned firms, Sirpa Paatero, to discuss Posti's plans to shift some employees to a different working contract agreed by another union. PAU says this would significantly cut the income of already low-paid staff members.
Tuomas Aarto, Director General of the Service Sector Employers' group (Palta), dismissed PAU's allegations of wage reductions, saying that the new contract would guarantee that all employees' current pay rate would stay the same.
"The breakdown in negotiations did not take place due to any single threshold question," he told Yle as he left the talks.
PAU chair Heidi Nieminen said after the negotiations that ensuring the income level of low-paid workers was the key issue for the union. She added that PAU apologises for the inconvenience for Posti customers caused by the industrial action.
Mail could be delayed by weeks
If the strike goes ahead as planned, package deliveries within Finland at least will be delayed.
"We're talking about delays of several days in the delivery of packages if the strike is carried out as it has been announced," said Jarmo Ainasoja, head of Posti's Control Centre.
The same goes for packages sent abroad, but Ainasoja said that much depends on how negotiations progress in the coming days.
Delays in letter mail may be significantly longer, even several weeks.
In a statement, PAU said it had "decided to take collective action to combat Posti's collective labour agreement shopping and the deteriorating of wages and conditions of employment," adding that "the strike does not prevent work related to the health and safety of citizens".
According to the trade union, Posti "has initiated various countermeasures to break the strike," telling its members that these "must be strictly rejected and reported immediately to the strike committee and to the union office!"