The refugees fled in three batches over the past four weeks from a camp for Iranian Kurds west of Baghdad.
"They have not been permitted to enter Jordan, nor to join another group of 660 refugees – mostly Iranian Kurds from al-Tash – who have been living in a camp in no-man's land between the two countries for the past year and a half," a UNHCR statement said on Friday.
The stranded refugees include at least five pregnant women and a large number of children.
Surviving on charity
The agency said the refugees "are believed to be surviving on the charity of passersby" but warned that this situation "will clearly not be tenable for much longer".
"Weather conditions at the border have been very harsh in recent days, with freezing temperatures and strong winds," the agency said, adding that it was seeking to provide them with supplies from Iraq.
The UNHCR "has so far not been permitted to bring assistance across from the Jordanian side", the statement added.
The agency said it would try to relocate the Iranian Kurds to northern Iraq or return them to al-Tash, a camp near the Iraqi cities of Falluja and Ramadi that has suffered from the volatile security situation in Iraq.
Jordan, already home to 1.7 million Palestinian refugees, has steadfastly refused to allow more refugees on its territory for demographic and economic reasons.
At the onset of the March 2003 US-led war against Iraq, Jordan set up a transit camp for refugees who have residency in third countries and a no-man's land border desert camp for all others.