WASHINGTON — The Trump administration said Friday it would bar the Chinese-owned mobile apps WeChat and TikTok from U. S. app stores as of midnight Sunday, a significant escalation in America’s tech fight with China that takes aim at two popular services used by more than 100 million people in the United States. In a series of moves designed to render WeChat essentially useless within the United States, the government will also ban American companies from processing transactions for WeChat or hosting its internet traffic as of midnight Sunday. Similar restrictions will go into effect for TikTok on Nov. 12 unless the company can assuage the administration’s concerns that the popular social media app poses a threat to U. national security. TikTok, which is owned by China’s ByteDance, is currently in talks to do a deal with the American software maker Oracle. The Commerce Department said the prohibitions could be lifted if TikTok resolves the administration’s national security concerns by the November deadline.“Today’s actions prove once again that President Trump will do everything in his power to guarantee our national security and protect Americans from the threats of the Chinese Communist Party, ” Commerce Secretary Wilbur Ross said in a statement. The actions follow an Aug. 6 executive order by Mr. Trump, in which he argued that TikTok and WeChat collect data from American users that could be accessed by the Chinese government. The administration has threatened fines of up to $1 million and up to 20 years in prison for violations of the order. TikTok spokesman Josh Gartner said in a statement that the company was disappointed in the Commerce Department’s decision.“We will continue to challenge the unjust executive order, which was enacted without due process and threatens to deprive the American people and small businesses across the US of a significant platform for both a voice and livelihoods, ” he said. Tencent Holdings, which owns WeChat, said in a statement it was reviewing the new rules and had submitted a proposal to address the government’s national security concerns about the app. It said it would “continue to discuss with the government and other stakeholders in the U. ways to achieve a long-term solution. ”Oracle did not immediately respond to a request for comment. Mr. Ross, in an interview on Fox Business Network on Friday morning, said that the ban would initially have a much greater impact on WeChat.“For all practical purposes it will be shut down in the U. S., but only in the U. S., as of midnight Monday, ” Mr. Ross said. TikTok would also face some changes, but would still be allowed to function until Nov. 12, Mr. Ross said, at which point it would face the same ban as WeChat if there was no deal that satisfied the administration’s concerns.“As to TikTok, the only real change as of Sunday night will be users won’t have access to improved updated apps, upgraded apps or maintenance, ” he said.