WASHINGTON (Reuters) -A Democratic senator on Monday asked U.S. President Donald Trump to answer key details about a plan by TikTok's Chinese owners to sell a majority stake in the short video app's U.S. assets. 

Trump signed an executive order on September 25 declaring that a plan to sell TikTok's U.S. operations to a consortium of U.S. and global investors meets the national security requirements set out in a 2024 law and gave them 120 days to complete the transaction. In doing so, he delayed until January 20 enforcement of the law banning the app used by 170 million Americans unless China's ByteDance sells it.

Senator Ed Markey said the White House has not answered numerous questions and has not followed the 2024 law.

"Your repeated unlawful extensions of the divestment deadline and vague comments about the deal raise significant questions about whether you have been able to secure an agreement that keeps TikTok online and addresses the national security concerns posed by ByteDance's ownership of TikTok," Markey said in a letter to Trump on Monday. 

"Congress and the American people need to understand the terms and status of this supposed agreement."

The White House did not immediately respond to a request for comment.

Trump's order said the algorithm will be retrained and monitored by the U.S. company's security partners, and operation of the algorithm will be under the control of the new joint venture.

Markey questioned if China had approved the deal, despite administration comments that it had.

"If TikTok U.S. is licensing the algorithm from ByteDance and retraining it, is this a one-time transfer of the source code or does TikTok U.S. have to renew it at regular intervals?" Markey asked. "Will any changes to the algorithm by ByteDance affect the algorithm that is licensed to TikTok U.S.?"

ByteDance would hold less than 20% in TikTok U.S. to comply with requirements detailed in the 2024 law.

U.S. Representative John Moolenaar, the Republican chair of the House Select Committee on China, said in October a licensing agreement for use of the TikTok algorithm, as part of the deal by ByteDance to sell TikTok's U.S. assets, would raise "serious concerns."