The Fair Trade Commission slapped a warning against Microsoft Corp. on Tuesday, demanding that the U.S. software giant remove what it said was an unfair clause from contracts with Japanese personal computer makers.

The largely symbolic move, which targets a patent-related provision that the FTC says violates the Antimonopoly Law, will not be backed by fines or other penalties.

But the move is important for Japanese manufacturers that develop digital devices, cell phones and other products that can replace personal computers, FTC director Toshihiko Hara said.