Welsh Secretary Peter Hain has claimed that Welsh police forces are too small to tackle the threat of terrorism, drug trafficking and organised crime.
The four Welsh police forces could be merged into one
Mr Hain said among many known terror suspects, some were in south Wales.
He has called for a single Welsh force to replace the existing four - although a BBC Wales poll suggests most people want them to stay as they are.
In an ICM poll of 1,000 adults for the Dragon's Eye programme, 58% backed the status quo, and 13% an all-Wales force.
Mr Hain had said on Wednesday that terrorist networks were "active" across south Wales, with "the potential to be so in north Wales" as well.
On Dragon's Eye, he expanded on these comments, to reinforce his argument that the "clear evidence" was that one police force was needed for Wales.
He referred to an arrest of a man in Cardiff recently, and said: "These people don't operate in isolation.
"I'm not saying that there is a cell waiting to pounce but there are networks right across Britain - hundreds of people involved that are known to the security service, some of them in south Wales.
"That being the case, we need a police force that is up for those challenges.
"And in certainly three and quite possibly all four (forces)... we don't have the ability to meet those challenges."
Mr Hain added on Friday: "The reorganisation is about establishing three important capabilities to meet the triple threats of terrorism, drug trafficking and serious organised crime.
"There are terrorist networks around - we all know that.
"The attacks on London in July came out of nowhere and they were British citizens. They are part of a wider network under surveillance and that includes people in south Wales.
"This isn't a question of frightening anybody, we all know there's a completely different world from what there was when the original four forces in Wales were established."
Top police officers told AMs this week that, on paper, one force would best meet UK government targets on tackling cross-border crime and terrorism - although they added they had not yet decided on a final option.
The debate over change follows calls by Home Secretary Charles Clarke for the 43 police forces in Wales and England to examine their set-up.
POLICE POLL RESULTS
Question: Do you think you would be better served if:
Four forces merged: 13% (128)
Merged into two: 10% (100)
Stay as they are: 58% (581)
Some other format (like merging with English forces): 7% (67)
Don't know: 7% (67)
ICM Research interviewed 1,000 adults by telephone from 31 Oct - 3 November
Her Majesty's Inspectorate of Constabulary has urged a cut in the number of forces, with the merger of some.
The four Welsh forces are North Wales, Dyfed-Powys, Gwent and South Wales, but the latter is the only one which comes close to the minimum recommended size of 4,000 officers.
The options are: merger of all four forces, creating two, or the status quo. North Wales Police Authority has suggested the possibility of merger with Cheshire Police.
The four forces were asked to respond to Mr Hain's comments.
Dyfed-Powys Police: "The force has been responding to the fluctuating terrorist threat for a number of years. We have been working together with the communities of Dyfed and Powys, and partner agencies in our combined efforts to deter and thwart terrorism.
"The events of 7 and 21 July in London reinforced the resolve to remain alert and vigilant to strive towards ensuring that our communities remain safe and secure."
Gwent Police: "The security status since 7 July has been enhanced. It's an effective measure to identify the risks and undertake proactive investigations to determine any terrorism threat."
North Wales Police: "We recognise a potential threat posed by terrorism and are constantly reviewing our intelligence and operational response."
South Wales Police: "There has been no specific threat against Wales and there is no intelligence to suggest that it is a potential target for any terrorist activity. The south Wales public need to be alert, but not alarmed, and report any suspicious activity to their local police station."