Russian units near Ukraine moved into "attack positions," official says

Russia has moved some long-range artillery and rocket launchers into firing position, threatening Ukraine, according to a U.S. official.

Some Russian units have left their assembly areas — the bumper-to-bumper formations seen in satellite photos — and are beginning to move into "attack positions," according to the official. This movement marks a change since Sunday, when some of the units had left the assembly areas but had not yet taken what could be viewed as attack positions.

The U.S. believes Russia will attack Ukraine by the end of the week, although it's not yet certain what form it will take, the official said.