Caution before Yellen's Jackson Hole speech crimps risk appetites

By Shinichi Saoshiro TOKYO (Reuters) - Caution ahead of a speech by Federal Reserve Chair Janet Yellen's speech at the annual gathering of central bankers in Jackson Hole, Wyoming, limited movements across global markets on Friday. Asian stocks tracked an overnight dip on Wall Street and edged down early in the session, while geopolitical tensions helped shore up crude oil prices. Risk markets were wary of the U.S. central bank hinting at near-term interest rate hike which could divert some of t