VILNIUS, Lithuania (AP) -- U.S. Vice President Joe Biden is warning Russia that the United States will respond to any aggression against NATO allies.
Biden told reporters during a visit to the Baltic region Wednesday that there are, quote, "growing costs that come with naked aggression."
Biden spoke a day after Russian President Vladimir Putin signed a treaty to annex Ukraine's Crimea region. The United States and other nations are calling that a violation of international law.
Biden says the United States takes its responsibilities under the NATO treaty to help defend member nations "very,very seriously."
Biden spoke at Lithuania's presidential palace after meeting with the presidents of Lithuania and Latvia.
(Please check back for updates to this developing story.)