During Wednesday's daily briefing, State Department spokesman Mark Toner said "There were some language issues".
"We're working to correct those, obviously, because it's important that we have Arabic speakers that were able to field incoming calls."
While parts of Syria are described as unusually calm since the cessation of hostilities began on Saturday, rebels say that government forces backed by Russian air strikes have continued offensives in strategic areas in northwestern Syria.
The US- and Russian-backed halt to the violence aims to provide breathing space so that peace talks can resume between the rebels and Syrian President Bashar al-Assad in the nearly five-year-long civil war in which more than 250,000 people have died.
Syria Direct, whose website describes itself as a non-profit journalism organization that covers Syria and trains aspiring Syrian and US journalists, published a story saying it called the hotline only to find an American struggling to speak Arabic.
The Amman-datelined story quotes Syria Direct reporter Orion Wilcox as saying he had called the hotline and had trouble making himself understood to the US official on the line.
"I didn't expect an American to answer; he answered in English but switched to Arabic. I started telling him in Arabic about reports we were getting from Homs province of specific ceasefire violations," Syria Direct quoted Wilcox as saying.
"He's really struggling and can't understand me," Wilcox added.
"I'm like, why is this American guy on the phone who can't speak Arabic?"
A US official who spoke on condition of anonymity said the hotline was set up in haste last week and the State Department had put out an email seeking volunteers to help staff it.
"People stepped forward ... my guess is that their Arabic just wasn't fluent enough," the official said, "So they were struggling to ... comprehend what was being told to them."
