The question as written is unanswerable. The Euphrates River is already west of the Iranian border, so any point west of the Euphrates is not part of Iran.
If the question meant to ask: What desert lies directly west of the Euphrates River in the southwestern part of Iraq? -- The answer would be the "Arabian Desert". North of the Arabian Desert and west of the Euphrates River, in northwestern Iraq is the "Syrian desert".
The Syrian Desert
The Syrian Desert and the Arabian Desert.
It is the arabian desert
desert rolling upland
Both the Tigris and Euphrates fit that description
desert rolling upland
Euphrates River
It is a river It was a river It will be a river It is spelled E-U-P-H-R-A-T-E-S It has water in it You just wasted your time reading this nonsense
The answer would be the "Arabian Desert". North of the Arabian Desert and west of the Euphrates River, in northwestern Iraq is the "Syrian desert"
The Euphrates River
The river that runs through Turkey, Syria, and Iraq is the Euphrates River.
The Euphrates river ends in Iraq