News Corp., moving to take advantage of growing international traffic to its MySpace Web site, confirmed plans for a joint venture with Softbank Corp. to operate a Japanese version of the popular social-networking site.

The joint venture follows News Corp.'s creation in recent months of local versions of MySpace in the United Kingdom, Ireland, Australia, Germany and France. These customized sites have helped increase MySpace's international traffic sixfold to 26.4 million unique visitors in the past year, according to September...