<p>Syrian rebel commander Hassan Abdul Ghany urged top military officers to defect, in a video statement aired on Friday.</p><p>In a further setback for Assad, a US-backed alliance led by Syrian Kurdish fighters has taken Deri el-Zor, the government's main foothold in the vast desert east of the country, three Syrian sources told <em>Reuters</em> on Friday.</p><p>It was the third major city, after Aleppo and Hama in the northwest and centre, to fall out of Assad's control in a week.</p>
<p>Syrian rebel commander Hassan Abdul Ghany urged top military officers to defect, in a video statement aired on Friday.</p><p>In a further setback for Assad, a US-backed alliance led by Syrian Kurdish fighters has taken Deri el-Zor, the government's main foothold in the vast desert east of the country, three Syrian sources told <em>Reuters</em> on Friday.</p><p>It was the third major city, after Aleppo and Hama in the northwest and centre, to fall out of Assad's control in a week.</p>