"Many have been living in limbo for years. This will increasingly be the case if states don't continue to welcome Iraqi refugees for resettlement," said Antonio Guterres, who is in Syria to mark World Refugee Day on June 20.
Guterres said around 52,000 Iraqis have been resettled, mostly in the United States, since 2007. The refugee agency has recommended another 48,000 should be accepted by host countries.
The bulk of refugee applications have come from Syria, Jordan, Lebanon, Egypt and Turkey, where most of the 1.8 million Iraqi refugees abroad live.
Pointing to Iraq, Afghanistan, Sudan and Congo as major conflict zones, Guterres said the proportion of refugees unable to return to their homes was rising because of the "growing resilience" of violence.
"Conflicts that we had hoped were on their way to being resolved are stagnating," he said.
Guterres said only 251,500 refugees out of a total of 15 million worldwide returned voluntarily to their homes last year, the lowest level in 20 years. Of those, 38,000 were Iraqi.
The United States took in three quarters of the resettled Iraqi refugees and 45 percent of those refugees submitted their applications from Syria, he said.
Washington came under pressure from international organizations and Europe to take in more Iraqi refugees after accepting only 1,200 in the 2007 fiscal year, which ends in September, but this still represented a large portion of the 3,500 Iraqis resettled from January to December 2007.
In Europe, Sweden has taken the lead in accepting Iraqi refugees, highlighting their plight on the European Union level.
Guterres, a former prime minister of Portugal, was speaking in the eastern province of Hasakeh, which borders Iraq and has been hit by consecutives droughts.
Despite tense ties with the US-backed Iraqi government, Syria has taken in hundreds of thousands of Iraqis who fled their homeland in the wake of the 2003 US invasion.
The invasion removed Saddam Hussein from power and ushered in sectarian bloodshed, displacing more than 4 million Iraqis.
The United Nations is organizing World Refugee Day in the Middle East for the first time. Guterres will join an event hosted by US Secretary of State Hillary Clinton in Washington via a video link from Hasakeh.
Relations between Washington and the Syrian government have improved since President Barack Obama took power last year, but Damascus remains under US sanctions.
