"It's sad, but I can understand his decision," coach Bengt-Ake Gustafsson said Thursday.
The 36-year-old Sundin, whose Toronto Maple Leafs missed the NHL playoffs, was one of the key players on Sweden's team last year when it won the Olympic gold medal.
Alexander Steen of the Leafs is the only NHL player who has accepted an invitation to play for Sweden so far, but several others are expected to join the squad.
Before the world tournament, Sweden will play Russia in a home-and-home series on April 19 and 21 for the European Hockey Tour title and a warmup against the United States in Stockholm on April 25.
The tournament is April 27-May 13 in Moscow, and Sweden is the defending champion.