Vice President JD Vance had in September said that the new U.S. company will be valued at around $14 billion.
Microsoft and TikTok did not immediately respond to Reuters' requests for a comment outside regular business hours.
TikTok CEO Shou Zi Chew plans to attend the U.S. presidential inauguration and attend a rally with Trump on Sunday, a source told Reuters.
TikTok and its Chinese parent, ByteDance, did not immediately respond to Reuters' requests for comment.