President Biden on Thursday said the U.S. has reason to believe that Russia is "engaged in a false flag operation," and said he believes that an invasion into Ukraine "will happen in the next several days."Tensions have spiked along the line that separates Ukrainian forces from Russia-backed separatists in the country’s east, with the parties accusing each other of intensive shelling.As he departed the White House, Biden said the threat of a Russian invasion into Ukraine is "very high," and that he believes it could happen "in the next several days." "They have not moved their troops out. They've moved...