President Trump welcomed President Recep Tayyip Erdogan to the Oval Office just weeks after Turkish forces stormed into Syria. But in Congress, there's a bipartisan push to punish Turkey.
Russia's military already has three of the S-400 "Triumf" divisions on the Black Sea peninsula; it plans to have another in place and operational by the year's end.
Turkey is scheduled to get its first F-35 jet fighters next week, but it is also considering buying Russia's most advanced anti-aircraft system. Congress is moving to block delivery of the warplane.