By Guy De Launey
BBC correspondent in Phnom Penh
A senior US government official has said Vietnamese Montagnards no longer suffer significant persecution.
Thousands of Montagnards from Vietnam's Central Highlands have poured over the border into Cambodia over the past three years to claim asylum.
They have made allegations of religious persecution and land grabs.
But Assistant Secretary of State Ellen Sauerbrey, speaking in Cambodia, said that few Montagnards should now qualify for refugee status.
Most Montagnards - members of ethnic minority groups in the Central Highlands - follow an evangelical branch of Christianity.
The influx into Cambodia began after the Vietnamese authorities cracked down on unlicensed churches three years ago.
Since then the United States has resettled hundreds of Montagnards, as have other countries including Finland and Canada.
But in recent months, the UN's refugee agency, the UNHCR, has been turning down an increasing number of applications for asylum and the US assistant secretary of state says it has been justified in doing so.
Ellen Sauerbrey told reporters that she had been able to meet freely with Montagnards in the Central Highlands.
They included some whose claims for refugee status had been unsuccessful.
She said there were no complaints of religious persecution and that the authorities were now taking a more relaxed approach towards local churches.
The current motivation for Montagnards crossing into Cambodia, she suggested, was largely economic.
But human rights groups have said there are still major concerns.
Last year Human Rights Watch accused the Vietnamese authorities of detaining and sometimes torturing returning Montagnards.