U.S. President Donald Trump signed a pair of executive orders prohibiting U.S. residents from doing business with the Chinese-owned TikTok and WeChat apps beginning 45 days from now, citing the national security risk of leaving Americans’ personal data exposed.

The bans mark a significant escalation by Trump in his confrontation with Beijing as the U.S. seeks to curb China’s power in global technology. With the U.S. election less than 90 days away, Trump is making his challenge of China a central theme of his campaign, where he trails Democrat Joe Biden in the polls.

Shares of WeChat’s owner, China’s Tencent Holdings Ltd., fell as much as 10 percent in morning trading. The offshore yuan weakened as much as 0.40 percent, the most since July 22, to 6.971 a dollar.