The UNHCR is to close several camps for Iraqi refugees in Iran because more than half of the 202,000 exiles have returned home.
The UNHCR has provided assistance to refugees determined to return home
The UN's refugee body said 42,000 out of 50,000 Iraqis at the centres had left since the fall of Saddam Hussein.
Six out of the UN's 22 camps in south Iran are empty and another two are due to close by the end of the month.
The agency has discouraged repatriation because of insecurity in Iraq and the border-crossing is riddled with mines.
About 107,000 refugees have left Iran since the former Iraqi leader was removed last year.
The camps were set up to provide shelter to fleeing Kurds and Shia Muslims, whose numbers peaked at two million at the height of the former Iraqi regime's repression.
There are still an estimated 95,000 Iraqis in Iran, making it the country with the largest Iraqi refugee population.
"UNHCR does not encourage Iraqis abroad to repatriate now, but we do provide assistance to refugees in some neighbouring countries who are determined to go back despite the difficult conditions inside Iraq," said spokeswoman Jennifer Pagonis.
She said that since last year, the agency had provided help to around 19,000 Iraqis who wanted to go home from countries around the Middle East.
Most of the Iraqis have returned by their own means and there have been several reports of people dying crossing the minefields on the border, according to the agency.