Danish police may struggle to control public demonstrations during the UN Climate Change Conference (COP15) as officers are expected to work 16 hours a day for the duration of the two-week event.

Police unions are concerned that officers will get mentally and physically exhausted due to the long work hours and that, as a result, security will suffer.

Large-scale demonstrations are likely to occur during the COP15 summit, which starts on Dec.7. Police will have manage that and provide security for the many state leaders present.

The Copenhagen Police has drafted in help from the regional police forces for the summit and Tom Steffensen, who is in charge Northern Jutland region's Police Union, is not impressed with the long hours expected.

Steffensen said to national newspaper Politiken that he feared police officers would make mistakes due to being tired and over-worked.

Regional union chief Steffen Daugaard, who leads the Funen region's union, is quoted in newspaper Berlingske Tidende: "These shifts are completely unfair. Nobody can handle that. And it means we will not have optimal security during the climate summit."

Jan Ovesen, a medical specialist who researches sleep patterns, concurs with the unions.

He warned that Police officers could get violent if they worked long hours and did not get enough sleep. If the officers have to deal with aggressive demonstrators all day, it would be difficult to for them to sleep because of the adrenalin, Ovesen said.

In total, 6500 police officers will provide security at the conference.