[Officials in the Trump administration on Sunday demanded Russia stop supporting the Syrian government or face a further deterioration in its relations with the United States.]
Russia annexed Crimea and the relationship deteriorated (not to mention various sanctions and other diplomatic repercussions).  Russia pretty much went all in on Syria when it started sending air craft and troops to support Assad.  This is long after Russia disregarded international agreements not to provide arms to Assad.  Every time a anything that would impact on Syria negatively came up on the UN Security Council Russia vetoed it.
So what exactly is the point of this proclamation?  It doesn't even amount to saber rattling.