The first-ever ThinkPad that converts to a tablet PC will make its debut on Monday, CNET News.com has learned.

China's Lenovo Group is expected to announce its new X41 Tablet Series (X41T) in coordination with IBM, which developed the convertible laptop. This is the first computer released by China's Lenovo Group following its purchase of IBM's legendary PC business earlier this year.

With its signature black casing, eraser-size trackball and red and blue click buttons, the X41 Tablet Series looks like any other model of IBM's ThinkPad laptop line.

However, the 12-inch screen of the X41T can be rotated 180 degrees and pressed flat against the computer's keyboard, turning the notebook into a tablet computer. This was made evident in photos and internal documents supplied by IBM's Japanese laboratories mysteriously that began appearing on the U.S. Federal Communications Commission Web site late last month.

A spokesman for Lenovo said the company would be making a major announcement on Monday but declined to elaborate. The spokesman also declined to comment on the IBM papers circulating on the FCC Web site.