Foreign demand for U.S. long-term investments soared in September, the Treasury Department reported Tuesday, as investors grew more confident about a recovery in the world's biggest economy. Net capital inflows into the United States jumped to $133.5 billion in September from an inflow of $25.3 billion the previous month. Long-term capital inflows—a key gauge of foreign investor appetite because it excludes short-term transactions—rose to $40.7 billion from $34.2 billion in August. Foreign investors' holdings of dollar-denominated short-term U.S. securities fell $11.8 billion, while overseas investments in Treasury bills fell $300 million.