Greg Kelly, who formerly headed the detention operations division of the Immigration Department and managed the regional office of the Bali Process on people smuggling, has taken up a position as counsellor in the Phnom Penh embassy, sources in Cambodia have told Fairfax Media.

Australia’s Ambassador for People Smuggling Issues, Craig Chittick, is expected in the country within days, fuelling rumours a deal is almost complete.

The Australian and Cambodian governments remain in secret negotiations over the arrangement.

It is not known under what conditions refugees will be sent to Cambodia, nor how much the government will pay the south-east Asian country for its assistance, although the figure of $40 million has been widely reported in both countries.

Foreign Minister Julie Bishop's office referred questions about Mr Kelly's appointment to Immigration Minister Scott Morrison, whose spokeswoman said there had been no recent developments regarding the Cambodia deal.

"The government is continuing its discussions on these issues and welcomes the receptive and positive response from Cambodia that has been provided to date," she said.

Government bureaucrats of both Cambodia and Australia have been briefing United Nations officials on the "general principles" of the proposed deal.

"But we have not seen any of the details," Vivian Tan, a spokeswoman for the office of the United Nations High Commissioner for Refugees, told Fairfax Media from Bangkok.

"We are concerned about some of the principles involved.

"Essentially this agreement involves recognised refugees being transferred from Australia, a convention country, to another country where they may not be able to enjoy all of their fundamental rights, but until we see the detail it's very hard to comment on this proposed arrangement."

The UN has said the deal is between Cambodia and Australia, and the UN would have no input into the agreement nor oversight of it.

Sources in Cambodia say the government will meet UN officials again next week.

The UNHCR office in Phnom Penh was downsized last year from 10 staff members to two, and more responsibility was handed to the Cambodian government-run Refugee Office.

Sister Denise Coghlan of the Cambodia Jesuit Refugee Service said that while the ideal situation would be for Australia to resettle the refugees, any Cambodia deal would need stringent and transparent safeguards.

"There should be no institutionalisation of these people, they cannot be locked up in a detention centre," she said. "And they need documentation right from the start. They need identification, they need proof of their status and their rights to work, and the children need access to education."

Sister Denise said Cambodia was a country tolerant of other religions and cultures, and that "between Nauru and Cambodia, I would choose Cambodia".

"But the state of mental health services in Cambodia is already overstretched, as the country tries to deal with its own genocide.

"At the moment, there are just not enough services to help even more traumatised people, particularly traumatised children, who are dealing with having to flee from their homeland and the extra suffering of being locked up on Nauru."