Provided by Dow Jones By Dawn Lim, Jing Yang and Gordon Lubold U.S. officials are considering prohibiting Americans from investing in Alibaba Group Holding Ltd. and Tencent Holdings Ltd., said people familiar with the matter. In recent weeks, State Department and Department of Defense officials have held conversations on expanding a blacklist of companies that are prohibited to U.S. investments because of claimed ties to China's military and security services. The U.S. government announced its original blacklist in November with 31 companies. The departments have debated with the Treasury Department over whether adding these firms could have wide capital-markets ramifications, the people said. The plan is still under deliberation and may not go through as agencies debate its impact on markets, the people added.