GB were due to face the Belarusians in Minsk on 25 February and fly to the former Soviet state for preparation a few days before that.
But tensions in the region around Belarus raised concerns for the safety of the team.
An emergency meeting of the British Basketball Federation (BBF) Board took place late on Saturday and decided, following consultation with staff and players, that the team should not travel to Minsk because of the potential risks involved.
FIBA confirmed the postponement of the game on Thursday as Russian troops entered Ukraine and fierce fighting took place.
“With the news reports of growing tensions in the region, the published advice of the Home Office, and a meeting to gauge the feelings and concerns of both the players and staff, the Board made the decision that the team’s safety and wellbeing is the only priority.”
“Guaranteeing player and staff safety is of paramount importance to us. Therefore, in collaboration with the BBF Board, we have regrettably had to make this decision.”
“We are happy that the welfare of the travelling group has been put first when making this difficult decision. It is every player’s dream to represent their country at senior level, but some things are bigger than basketball and the current situation in that part of the world is extremely worrying. We look forward to working with FIBA to deliver a practical solution as soon as possible.”
The Belarus team is due to travel to the UK to face GB in the return leg of the fixture at Newcastle Vertu Motors Arena on 28 February.
This article was updated on 24 February.