Japanese national telco Nippon Telegraph and Telephone Corp is planning to invest $100m in Teligent Inc, a US wireless telecoms venture, reports the Nihon Keizai Shimbun. The $100m will buy NTT a 15% stake in the Teligent venture which is owned by Associated Communications LLC. Alexandria, Virginia-based Teligent is a headed by former president and chief operating officer of AT&T Corp, Alex Mandl. The company has ammbitious plans to connect half the US population to its wireless network by 2001, and starts its commercial service in 1998.