NEW YORK, May 4 : The U.S. dollar rose against the euro as the conflict in the Middle East kept investors skittish and the yen briefly strengthened prompting renewed speculation about intervention by Japanese authorities. The dollar index, which measures the U.S. currency's strength against a basket of currencies, was 0.2 per cent higher at 98.404. The index, which has slipped from the highs reached in the immediate aftermath of U.S. strikes on Iran in early March, continues to find support in