Welsh police chiefs have said that on paper an all-Wales force would best meet government targets for tackling cross-border crime and terrorism.
Wales' four police forces could be merged into one
But they will not say if they back that option or not.
The chief constables of the four Welsh forces met Assembly Members to discuss police restructuring to tackle cross-border crime and terrorism.
Meawhile, Welsh Secretary Peter Hain has reiterated his preference for an all-Wales force.
But he said there should still be an element of regional accountability.
Merging smaller forces
Attempts to restructure the police follow calls from Home Secretary Charles Clarke for all police forces in Wales and England to examine the way they are organised.
A report in September by Her Majesty's Inspectorate of Constabulary called for a reduction in the number of forces across Wales and England, with the merger of some smaller forces.
The options for Wales are to merge all four police forces into one, reduce the four forces into two separate bodies, or to leave things as they are.
North Wales police authority also wants a fourth option to be considered, whereby the North Wales force would merge with Cheshire police.
Speaking on behalf of his fellow chief constables, Terry Grange of the Dyfed-Powys Police, said they had not decided on a final option, but that a single force was the best option.
The director of the Welsh Local Government Association (WLGA), Steve Thomas, said: "The timescale is lunatic and everyone knows that.
"We're working in a context set by the Home Office and making the best of a bad job," he said.
Mr Thomas said the WLGA had not decided on which option it thought was best, but said that no change seemed unlikely.
Geraint Price-Thomas, chairman of Gwent Police Authority, also expressed concern that there was "a political drive" to push through the changes quickly, which he said was causing "tremendous difficulty".
The treasurer of Dyfed-Powys Police Authority, Jean Wilding, told the assembly committee that "significant additional central resources would be needed".
She said that if these costs were not met by central government, "there would be a very substantial impact on council tax levels".
Police authorities in Wales will make a decision on their preferred option by the end of November.
It is expected that the home secretary will make his decision at the end of December.