The strike will be launched unless already agreed but still outstanding commitments are met, said the bigger of two trade unions bringing together police and Interior Ministry employees.

The union says the government has "endlessly and without justification deferred the fulfilment of commitments," while the current refugee crisis "cannot be an excuse" not to honour these commitments.

It is precisely because of the refugee crisis that the government has been given 20 days for a deal on the fulfilment of commitments, the union's boss Radivoj Uroševič said.

The announcement caps months of low-level activity by the union, which formed a strike committee in late August.

The demands refer to agreements made with previous governments in 2010, 2012 and 2013, most of which have been deferred due to years of austerity measures and sluggish economic growth in the past.

The union claims these commitments were made conditional on GDP growth and would now have to be implemented as of 2016.

Uroševič said implementation should lead to pay increases in the force of 26-35%.

Police strikes are circumscribed by law, as officers need to continue providing protection of people and property.

According to Uroševič, the union would comply with the limitations, as the officers do not want to erode security in this "critical time."

The government can still stop the strike if it immediately approaches the union with an appropriate deal, he said.

The police leadership said it stood by the union and understood officers' complains, as austerity measures have affected officers' workload.

But the strike may not undermine the security situation as police work is crucial due to the refugee crisis, according to a statement from the General Police Directorate.