Tokyo stocks opened lower Tuesday on rising tensions between the United States and Russia over Ukraine, while investors remained cautious ahead of a two-day U.S. Federal Reserve policy meeting later in the day. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average fell 293.20 points, or 1.06 percent, from Monday to 27,295.17. The broader Topix index of all First Section issues on the Tokyo Stock Exchange was down 22.38 points, or 1.16 percent, to 1,907.49. Every industry category lost ground, led by air transportation, marine transportation and service issues. At 9 a.m., the d…