Austrian Defence Minister Gerald Klug also demanded UN guarantees that the observers can be rotated and get supplies via Syria.
"I demand from the UN that we get assurances that supplies and troop rotations are possible via Syria. In addition we demand that the contingent that is being withdrawn by Croatia is replenished by the UN," he was quoted as saying.
Japan announced its withdrawal from UNDOF three months ago due to the violence in Syria. Croatia said last month it would also pull out its troops as a precaution after reports, which it denied, that Croatian arms had been shipped to Syrian rebels.
The vulnerability of the 1,000-member UN peacekeeping force on the Golan was highlighted last week when Syrian rebels detained 21 unarmed observers, all Filipinos, for three days.
Asked whether there were evacuation plans for the Austrians, Klug called this a "very sensitive subject".
Once the Croatians leave, UNDOF will have contingents only from Austria, India and the Philippines. A senior Western diplomat has said Manila is considering pulling its troops out.
Croatian Prime Minister Zoran Milanovic said in late February that Croatia would pull out its 97 observers from the Golan because their security could not be guaranteed after foreign media reports that Croatia was allegedly selling weapons to Syrian rebels.
"This exposes our troops to unpredictable risks. Our responsibility and task is to think about that and act when necessary," he said.