Simmons had already withdrawn from the FIBA World Cup squad to prepare for the next NBA season after signing a new five-year, $US170 million ($A241.6m) contract with Philadelphia 76ers but still planned to play in the four warm-up games next month.

However Basketball Australia announced that after discussions with coach Andrej Lemanis he would no longer take part in the exhibition matches.

The Boomers play Canada in exhibition games in Perth on August 16 and 17, and then face the United States in Melbourne on August 22 and 24.

The pair decided it was better for the Australian team's preparation for the tournament, starting in China in late August, if he didn't play.

Currently in Melbourne to host a junior training camp, Simmons said he was still committed to playing for Australia in next year's Olympics.

"After talking with coach Andrej, we both agreed it was better for me to not participate in this year's 2019 World Cup and exhibition games," Simmons said in a statement on Sunday.

"With our focus being to win a medal at the 2020 Olympics, the Boomers' preparation in the lead up to the world championships is of the utmost importance and me not playing allows the team to create the chemistry they need to compete at the highest level and qualify for the Olympics.

"I want to thank Basketball Australia for their continued support and I'm committed and excited to compete in the 2020 Olympics in Tokyo."

Senior Boomer Patty Mills said that the team understood the decision for Simmons not to play.

"We as his teammates respect his decision and we understand his situation has changed," Mills said in the statement.

"We appreciate his continued support and willingness to still be a valuable part of the team as we prepare for our ultimate goal of winning a medal at the World Champs for the first time."

A replacement for Simmons in the 18-man squad will be announced on Monday.

Australian Associated Press