CAMP DAVID, Md. (Reuters) - President Barack Obama and Gulf leaders were to discuss strategies for Syria on Thursday, White House deputy national security adviser Ben Rhodes told reporters at a briefing. The White House is open to evaluating the option of a **-fly zone to help with the Syrian conflict, Rhodes said, although he said the measure is **t seen as a viable way to address fighting in urban areas. The White House has **t independently verified new reports of chemical ******* use in Syria, Rhodes said. (Reporting by Roberta Rampton, Jeff Mason, Susan Heavey; Editing by Bill Trott)