Russia says it invaded Ukraine to halt Kyiv's ambitions to join NATO, the U.S.-led defensive alliance, which it saw as a major security threat. It also accuses Kyiv of persecuting ethnic Russians and their culture in Ukraine.

The U.S.-Russia summit in Alaska is happening where East meets West — quite literally — in a place familiar to both countries as a Cold War front line of missile defense, radar outposts and intelligence gathering.