Lebanon urged to unblock permits for UN Syria refugee staff
The decision was announced on Friday by the office of Lebanese Foreign Minister Gebran Bassil who has accused UNHCR of intimidating refugees to prevent their return to Syria.
Speaking to reporters in Geneva, UNHCR spokesman Andrej Mahecic said the agency was "very concerned" by the move.
"We hope the decision of the foreign ministry will be reversed without delay," he said.
Bassil had on Thursday pointed the finger at the agency in a posting on Twitter.
"We sent a mission that verified that the UNHCR is intimidating the displaced who wish to return voluntarily," he tweeted.
UNHCR has denied the allegations but made clear it does not believe the conditions in Syria are "conducive for an assisted return" - although a spokesman said the situation was changing and that the agency was following developments.
Lebanese Prime Minister Saad Hariri had immediately moved to disassociate himself from the move, with his office describing it as "unilateral" and "not representative of the Lebanese government's position".
There are an estimated 1.5 million people displaced by the war in neighbouring Syria in Lebanon - a figure representing more than a quarter of its population before the conflict.