Russia and Iran's 'unprecedented' military ties worried the US, but it's starting to look like Russia can't hold up its end of the deal

• Iran has supported Russia by providing it with arms to use in Ukraine.
• That has worried the US, which sees it as part of a growing Russian-Iranian defense partnership.
• But there are signs that Moscow may not deliver on the agreements it has made with Tehran.

Less than a year ago, the White House was warning of "unprecedented" military ties between Russia and Iran, but today, there are signs of increasing friction, with Moscow proving to be an unreliable partner.