A US-funded militia in the Afghan province of Helmand is to be expanded, provincial governor Golab Mangal says.
Mr Mangal told BBC Pashto that local armed groups of civilians were an important weapon in the struggle against the Taliban.
About 800 armed men are now being directly funded by the US in Helmand province, which makes them a larger force than the official police.
But they have been criticised for being heavy-handed and unaccountable.
In some cases, critics say, they have apparently been infiltrated by the Taliban.
But Mr Mangal played down the dangers of this happening.
"I give my people full assurances," he said.
"The moment these local forces mistreat people or fail to obey the law, they'll be dealt with. There'll be strict control of them.
"Their job is only to look after the security of their own areas. They don't have any other responsibilities, like running checkpoints or search operations. That's the job of the national police."
The BBC's Jill McGivering says that the governor's comments contradict some Western media reports that the programmes might be reduced because of concerns about their growing influence and lack of accountability.
Our correspondent says that local anti-Taliban defence forces have been hailed as an important part of the government's security strategy in Afghanistan.
Paid per person by the US, these militia now operate in several of the country's most violent provinces.
Mr Mangal said that while they had proved successful in Helmand, there was a possibility they could be infiltrated by the Taliban because the militia fighters may come from areas which sympathise with the militants.
He warned that if there was no proper control of the recruitment process, there was also a danger that those joining the militias might turn to crime or other anti-social and illegal activities, including harassing local people and theft.
"That is a possibility. But so far we've adopted very serious control measures," he said.