The U.S. put sanctions on Russia’s main arms exporter, Kremlin aides and the black leather-loving head of a motorcycle gang nicknamed “The Surgeon” after the 2014 invasion of Ukraine.

Now, as Washington seeks ways to punish Moscow for its actions in Syria, it may be running out of options.

The Obama administration says that new sanctions are among its alternatives as it seeks to ease the humanitarian crisis in Syria, where Russia backs President Bashar Assad’s drive to recapture the city of Aleppo.

“There’s nobody left to sanction in Russia besides the janitor in the Kremlin,” said Michael Kofman, a fellow at the Wilson Center’s Kennan Institute. “In terms of expanding any kind of commercial or financial sanctions, we’re basically maxed out.”

Penalties against Russia already include hundreds of people, from senior allies of President Vladimir Putin to the Night Wolves, a motorcycle gang led by a former medical student accused of aiding Russian forces in Ukraine. The State Department issued an exemption from sanctions on Russia’s main weapons exporter because restrictions made it impossible for Afghan security forces to get parts for their Russian helicopters.

If the U.S. wanted to truly damage Russia’s economy, it could bar American banks from buying Russian ruble bonds. The “nuclear option” would be an embargo on Russian energy exports. The U.S. official said that option wasn’t on the table. Europe gets about one-third of its energy supplies from Russia.