MOSCOW — In his toughest moments, President Nicolás Maduro of Venezuela has turned to Russia for support.

When the United States sanctioned the Venezuelan energy industry in January, Russia’s oil firm Rosneft helped to divert its oil exports to Asia. And when rumors of an armed American intervention reached fever pitch in March, two airplanes with Russian military technicians landed in Caracas — a reminder Russia was on Venezuela’s side.

Yet there is growing evidence that, beyond these high-profile gestures with limited effect on the ground, economic ties between Venezuela and Russia are fraying. Russian banks, grain exporters, even weapons manufacturers have all curtailed business with Venezuela, driven away by the very economic collapse they intended to help Russia’s South American ally withstand.

“Russia’s economic ties to Venezuela have really slowed down in the past few years,” said Maximilian Hess, a fellow at the Foreign Policy Research Institute in London. “The policies today are really low-cost, but they get a lot of geopolitical play.”