The European Central Bank’s signal that more stimulus is coming for Europe’s economy could complicate the U.S. Federal Reserve’s own message this week about when it might move in the opposite direction. ECB President Mario Draghi caused the dollar to jump against the euro on Thursday when he said the ECB was studying new ways to fight off deflation and spur growth that may be announced as soon as December. The Fed was already treading cautiously about whether it would begin raising U.S. interest rates in December.