Russia's point man for arms control cautioned Donald Trump's incoming administration on Friday against resuming nuclear testing, saying Moscow would keep its own options open amid what he said was Washington's "extremely hostile" stance.

Russia warns of potential nuclear testing in response to Trump's stance, raising concerns about global security.

Deputy Foreign Minister of the Russian Federation Sergei Ryabkov said American policy is "extremely hostile" toward Russia.

Is the world nearing a nuclear showdown? Russia has issued a dire warning to the U.S., raising concerns about the future of the Comprehensive Nuclear Test Ban Treaty. Russian Deputy Foreign Minister Sergei Ryabkov has called U.