International Business Machines Corp. and Sun Microsystems Inc., longtime rivals, said IBM will become the first major hardware vendor to resell Sun's Solaris operating system.

The deal will allow IBM customers to buy Solaris on selected Big Blue server systems, starting with those that use the x86 chip design offered by Intel Corp. and Advanced Micro Devices Inc. IBM and Sun executives added that the software may later be offered on IBM's popular mainframe systems.

Such...