Report to call for Wales' 22 councils to merge
A key report will call for Welsh councils to be re-organised through mergers, BBC Wales understands.
On Monday the Williams Commission is expected to suggest existing local council boundaries as the "building blocks", not new lines on the map.
New councils should also be within current health board and police force areas, the report is understood to say.
The commission is expected to call for a cut in the number of councils in a wide-ranging review of public services.
The report, by former NHS Wales chief executive Paul Williams, is expected to consider how many areas of public services can be improved and made more accountable to the people who use them.
The recommendations on the future of local authorities are expected to fire the starting gun for the first council re-organisations in Wales in nearly two decades.
Respecting existing health board and police force areas would mean Bridgend council would be unlikely to merge with the Vale of Glamorgan, for example, because the authorities are covered by different health boards.
The report is expected to suggest that the new council borders should not cross the geographical areas governing eligibility for EU aid, meaning Blaenau Gwent, which is entitled to the greatest financial assistance, would not be likely to merge with Monmouthshire, which is not.
In a BBC interview for this weekend's Sunday Politics Wales programme, First Minister Carwyn Jones said the existing number of 22 local authorities was "too many".
"I think the structure that was put in place in '95 was an unsustainable structure," he said.
"The question now is what will the Williams Commission recommend and we look forward now to seeing their recommendations in the course of this week."
Asked if councils would have avoided a reorganisation if they had worked together and shared services better, Mr Jones said: "No. I think it would have helped but I don't think it would have been possible.
"When you have some very small councils there are capacity issues that are very difficult to address.
"We have, at the last count, six local authorities who are in special measures with regard to education out of 22.
"Now that's not sustainable in the future so we need to have a very hard, long and honest look at the structure of not just local government but all public services in Wales, to make sure that the structure is far more sustainable and stronger in the future," added Mr Jones.
"People realise that's a capacity issue and I think the cutbacks agenda has actually highlighted that.
"But whether shoe-horning local government into seven health authorities in four police authorities that don't make sense is another matter."
But Jeff Jones, a local government consultant and former leader of Bridgend County council, accused the Williams Commission of producing "Welsh fudge".
"The seven health trusts are not actually working, the four police authorities don't work - Gwent shouldn't be there," he said.
"The problem in this country, not just in Wales, is that we haven't got local government, we've got local administration.
"What do you want local government to do is the big question and when you answer that then you produce the structures.
"The Williams Commission has such a short timescale you can't expect anything from it and this is what you've got - typical Welsh fudge."
Sunday Politics Wales is on BBC One Wales at 11:00 GMT on Sunday.