What countries were involved in the U-2 Incident?

There were quite a lot of U-2 incidents, but the one generally called "The U-2 Incident" occurred in the final year of the Eisenhower administration. After repeated accusations from the Soviet Union that American spy planes were invading their space, and America's repeated denials, the Russians shot down a U-2 flown by Francis Gary Powers deep inside Russia. The resulting publicity caused the two countries to cancel an important series of arms reduction talks.