Just four months after Apple breached the US$1 trillion mark, the iPhone maker has lost its lead as Wall Street's most valuable company and is on the verge of being replaced by Microsoft.
Buoyed by a broad rebound in US stocks on Monday, Microsoft jumped 3.11 percent to US$106.28, pushing its market capitalisation up to a record US$816 billion at mid-day. At the same time, shares of Apple rose 0.63 percent, leaving its stock market value at US$823 billion.
Earlier, Apple's stock fell, and both companies' market capitalisation were within about US$3 billion of each other, putting them at virtually the same value.
Technology shares have been punished in recent months as investors worry about rising interest rates and fallout from a trade conflict between the United States and China.
But Apple has suffered more than other Silicon Valley stalwarts, down 23 percent since it warned on 1 November that sales for the crucial holiday quarter would likely miss Wall Street expectations.
Global demand for smartphones has slowed in recent years, making it more difficult for Apple to increase its revenue.
Apple's market capitalisation overtook Microsoft's in 2010 as the maker of Windows software struggled with slow demand for personal computers, due in part to the explosion of smartphones driven by the iPhone.
(Reporting by Noel Randewich, additional reporting by Charles Mikolajczak and Lewis Krauskopf in New York; Editing by Marguerita Choy)