TOKYO, June 1 (Reuters) - Japanese Economics Minister Hiroko Ota said on Friday the government needs to closely watch signs of underlying weakness in the U.S. economy and how it could affect Japan. "Overall, the U.S. economy seems to be heading towards a soft landing. But it's showing an underlying weakness, which may have led to a decline in Japan's automobile output," Ota told a news conference. U.S. economic growth in the first quarter was the weakest in more than four years, data