By Timothy Gardner WASHINGTON (Reuters) -U.S. President Joe Biden’s global energy security adviser said on Monday that Russian President Vladimir Putin is getting close to using natural gas as a political tool if Russia is holding back fuel exports to Europe as it suffers an energy crunch. “I think we are getting close to that line if Russia indeed has the gas to supply and it chooses not to, and it will only do so if Europe accedes to other demands that are completely unrelated,” Amos Hochstein, Biden’s adviser, told reporters, when asked if Putin was using gas as a weapon. Hochstein said gas…