"The plane carrying the official Syrian delegation has been blocked for three hours at Athens airport because the Greek authorities refuse to provide it with fuel," the source said.
In Athens, a civil aviation spokesman confirmed to AFP that the plane was blocked but insisted it was leaving soon.
"The plane has been in Athens' airport for about four hours. There is a problem of refuelling that is going to be resolved soon and the plane is going to set off," a civil aviation spokesperson, who declined to be named, told AFP.
The civil aviation spokesman said the plane was being inspected and had not submitted a flight plan.
"Overall it will take about five hours," to complete the procedure, the spokesman said. "The plane has already been here for three or four hours."
Greece's ANA news agency reported that authorities were following inspection procedures required for countries facing international embargoes, such as Syria.