Russia: "Not much cause for optimism" amid Ukraine crisis

(Moscow) -- Russia warns there's "not much cause for optimism" as it weighs a possible invasion of Ukraine.  

The comments from the Kremlin come as President Vladimir Putin reviews written responses from the U.S. and NATO to its security demands. Putin has demanded assurances that Ukraine will never become part of NATO, but the U.S. has so far held firm on Ukraine's right to join.  

The U.S. asked the Kremlin to keep the letter confidential.