A video surfaces threatening the Winter Olympics. Russia's President vows the Games will be safe. Some U.S. lawmakers warn that they won't be.

One thing was clear as debate over the situation surged on Sunday: Security is a top concern, less than three weeks away from the competition.

"It's a very serious fear," Sen. Angus King, I-Maine, told CNN's State of the Union Sunday.

A video that highlighted the security situation has surfaced online. In the video, posted on a well-known Jihadi forum website, two young men believed to have been suicide bombers in last month's back-to-back bombings in the Russian city of Volgograd speak of those attacks and make an ominous promise.