The prospect of a single police force for the whole of Wales has been raised by a report which calls for smaller forces in England and Wales to merge.
North Wales is resisting the prospect of a single Welsh force
Her Majesty's Inspectorate of Constabulary (HMIC) says the current set up is unfit for the 21st Century.
The Police Federation said it accepted the number of forces was likely to be cut from the current 43.
Also mooted is the possibility of amalgamating Dyfed-Powys and Gwent forces into a bigger south Wales force.
Talking about the prospect of an all-Wales force, the chairman of North Wales Police Authority said it would be "almost impossible".
Ian Roberts said: "I accept the mergers should come but in reality, for north Wales, we should be merging with the north west (of England) rather than the whole of Wales.
"I realise and everybody else realises that is not politically possible."
He said most of the criminals the force dealt with came from Cheshire and Merseyside.
The HMIC report, published on Friday, raised speculation that some Welsh forces may be merged - perhaps even forming a single force in Wales - as part of a radical shake-up of British policing.
It argues that forces below a certain size do not have sufficient critical mass to respond effectively, while the bigger forced tended to be better at tackling terrorists, and dealing with serious crime and organised crime.
A large force is defined as one with more than 4,000 officers. Wales' largest forces is South Wales Police which has fewer than 3,500 officers, while none of the other three have more than 2,000 each.
None of Wales' four forces are classed as big by the report
Creating a police force that had 4,000 officers in Wales could mean a merger of the Gwent, Dyfed-Powys and north Wales forces.
Its responsibilities would stretch from the Severn to the Dee, and from Holyhead to St David's.
North Wales Police appears to be lining up to fight any possible merger.
Deputy chief constable Clive Wolfendale said his force already shared facilities such as helicopters and diving units with the Cheshire force.
He said: "This is a very successful organisation and we want to keep it that way.
"We are already collaborating on a number of issues, with forces within Wales and outside, on operational things, financial, procurement, and that can be developed.
"I think for me at the moment that's where the future lies, in actually looking for successful collaborations on individual or groups of forces on different issues.
"What makes sense in one area, might not in another."
On Monday, all the chief constables from Wales and England are the meeting Home Secretary who will give more detail on his plans.
Alan Gordon, the vice chairman of the Police Federation, which represents rank and file officers, said he accepted there would have to be fewer forces.
He said: "Policing crime has changed. Criminals have become more professional, it's more technical.
"We have to accept that there are some forces that just do not have the capability to respond to major criminal activity.
"I think we recognise that (merging some forces) may be a way forward to overcome those problems."