"Coalition strike on the governmental Syrian forces is an attempt to prevent the Syrian Army from advancing and taking control over Iraqi-Syrian border," Ahmad said.
According to the official, the coalition first aimed to "help Daesh [IS] to acquire control over cities on the border and Deir ez-Zor is a capital of this province."
"Later, they would replace Daesh fighters with rebels under their control or troops that belong to the states within the US-led coalition such as Turkey or Jordan. The idea is to cut off Syria from Iraq and to create a buffer zone," Ahmad said.
Syria has been mired in civil war since 2011, with government forces fighting numerous opposition factions and extremist groups, including the Islamic State (IS), which is outlawed in many countries, including Russia. The government-held city of Deir Ez-Zor has been under siege from IS since July 2014.
The US-led coalition has been carrying out anti-IS strikes since September 2014 without Syrian government consent.