By Kaori Kaneko and Doug Palmer TOKYO/WASHINGTON (Reuters) - Japan and the United States have agreed on a deal to allow Tokyo to join talks on a U.S.-led Asia-Pacific free trade pact that Prime Minister Shinzo Abe is making a keystone of his strategy to open Japan's economy and spur long-sought growth. The agreement brings Japan closer to entering talks on the Trans-Pacific Partnership (TPP), which Japan hopes to participate in as early as July. ...