ISTANBUL — With empty pockets and clothes smudged with dirt, the Syrian rebel fighter smuggled himself across the border and traveled 18 hours by bus to plead with Syrian opposition leaders meeting in a luxury hotel here to send help back home.

The fighter, Hassan Tabanja, a former electrician, needed money to provide food, weapons and ammunition for dozens of men fighting alongside him against the government of President Bashar al-Assad. But after two days of scant results at the main opposition coalition’s meeting here last weekend, Mr. Tabanja sat on the patio glaring at the men in suits all around him.

What they had provided, he said, “will barely get me back to Syria.”

For Mr. Tabanja and many other government opponents inside Syria, the leaders of the coalition who claim to represent them abroad have long seemed detached from their suffering, and frugal or mysterious with the money they have raised. As the leaders have shuttled among world capitals and bickered in fancy hotels, they have appeared increasingly powerless to affect the course of Syria’s war: more than 100,000 people have died, millions have been displaced, and extremist groups are gaining ground.

The leaders complain that their efforts to win recognition and support have been thwarted by the world’s indifference and the competing agendas of their own tightfisted patrons, but their words have failed to assuage many of the people relying on them for help.