US citizen, Mayer, one of TikTok’s key counter arguments that the app was already US-based and not a surveillance tool of the Chinese government.
The wildly popular video app allows users to create and edit short videos.
The US military has already banned its use.
Trump has called for ByteDance to sell the app, likely to Microsoft, by mid-September, with any non-US roles shut down by November.
TikTok CEO Kevin Mayer resigns after Trump threatens to ban app.
An American citizen, Mayer was part of the Chinese-owned company’s key arguments that TikTok is based in the US.
General Manager Vanessa Pappas will replace him on an interim basis, according to company law practices.
“In recent weeks, as the political environment has sharply changed, I have done significant reflection on what the corporate structural changes will require, and what it means for the global role I signed up for,” Mayer said in the letter.
ByteDance, which owns the popular app, said in a statement that it hopes to quickly resolve the business hurdles that it faces in the US.
Washington claims that Chinese-owned ByteDance could be sharing private user data with Beijing and poses a national security threat. Trump has given ByteDance until November 12 to spinoff or sell TikTok.