WASHINGTON (Reuters) - The Federal Communications Commission (FCC) said Wednesday it has begun efforts to revoke authorization for China Unicom Americas, Pacific Networks and its wholly-owned subsidiary ComNet to provide U.S. telecommunications services. In April, the U.S. telecom regulator issued show-cause orders warning it might revoke the operating licenses of three state-controlled Chinese telecommunications companies - the two cited on Wednesday and China Telecom Corp Ltd. China Unicom Americas has a two-decade old authorization to provide U.S. international telecommunications services. The carriers did not immediately respond to requests for comment. The FCC said Wednesday the companies “have failed at this stage to dispel serious concerns” about their U.S. authorizations. The regulator opened a similar proceeding in December to begin revoking the authorization of China Telecom, the largest Chinese telecommunications company, which has had U.S. authorization for nearly 20 years. FCC Commissioner Geoffrey Starks noted many Chinese telecom carriers “also own data centers operating within the United states.” He said the FCC currently lacks authority to “address this potential national security threat.” In May 2019, the FCC voted unanimously to deny another state-owned Chinese telecommunications company, China Mobile, the right to provide U.S. services, citing risks that the Chinese government could use the approval to conduct espionage against the U.S. government. The FCC has taken a hard line against Chinese telecommunications. On Friday, the FCC designated five Chinese companies as threats to national security under a 2019 law aimed at protecting U.S. communications networks. The FCC named Huawei Technologies Co, ZTE Corp, Hytera Communications Corp, Hangzhou Hikvision Digital Technology Co and Dahua Technology Co. In April, the FCC approved Alphabet Inc unit Google’s request to use part of a U.S.-Asia undersea telecommunications cable, but not to Hong Kong. Last week, Facebook withdrew an application to use a cable to carry internet traffic between the United States and Hong Kong, citing “ongoing concerns from the US government about direct communications links.” In September, Facebook, Amazon.com Inc and China Mobile withdrew their application to connect San Francisco and Hong Kong as part of the Bay to Bay Express Cable System.