Driving southbound on I-25 just south of the Wyoming/Colorado border, I observed an unusually large, bright star-like light in the sky. I noticed the bluish-white ball of light because it was rising vertically from behind the the mountains Southwest of F.E. Warren Air Force Base. It slowly rose vertically and my first thought was, "Large stars do not move and they do not travel vertically". That's when I decided to stop on the shoulder and watch what this ball of light was doing. I slowed down and stopped. As I got out of the car, the ball of light stopped and then hovered for about minute. I thought, "Now wait a minute! This is truly unusual". Then, the ball of light took off at a 45 degree angle headed north. The speed at which it took off from a dead stop was incredible! In two seconds, the light was gone. I said to myself, "I think I just witnessed a UFO". I never reported this sighting, fearing that the FBI might want to talk to me. I never told anyone because I thought my friends might think I was crazy. About 5 years ago, I told my best friend, asking him not to reveal my secret to anyone. He has been encouraging me to report the incident. I found out recently that there is a MUFON office in Ft. Collins, Colorado. I hesitate to go there in person, so this is my report.