GLOBAL MARKETS-Stocks pause, dollar jumps on Yellen comments, Ukraine

* Dollar rise lifts greenback index to 2014 high * Russia convoy enters Ukraine * Yellen urges caution on rates moves (Adds latest prices, quotes) By Michael Connor NEW YORK, Aug 22 (Reuters) - Wall Street and other stock markets paused while the dollar rose on Friday after Federal Reserve Chair Janet Yellen said policymakers eyeing interest rate hikes need to move cautiously, while worsening Ukraine tensions dogged trading. Ukraine on Friday said Russia had launched a "dir