Photo Palmyra, Syria, in March 2014, before it fell to militants of the Islamic State. Credit Sergey Ponomarev for The New York Times Two top United Nations relief officials expressed growing frustration on Wednesday over the organization’s inability to deliver aid to destitute Syrians trapped by war, saying that the number of besieged areas has risen to 18 from 15 in the past few weeks and that nearly half a million people may be at risk of starving to death. The officials, Stephen O’Brien and Ertharin Cousin, delivered their warnings to the United Nations Security Council two days before the scheduled convening of talks in Geneva aimed at halting the war in Syria , which has raged for nearly five years. Whether those talks will proceed as hoped remains unclear. Mr. O’Brien, the United Nations emergency relief coordinator, told Council members that roughly 4.6 million people lived in besieged […]