The British team now need to beat to Group A bottom side Austria in their final group game on Saturday lunchtime, and hope that other results go their way if they are to reach the quarter-finals.
Mary Durojaye led Britain with 16 points and 11 rebounds, while Harriett Yea finished with 15 points and five boards. Tamzin Barroilhet and Charlotte Stoddart also finished in double figures with 11 and 10 points respectively, with the latter also collecting five steals as Britain continued their improved form.
Kim Mestdagh led Belgium with 25 points, with Charlotte Ippersiel added 15 points - with both players pulling down eight rebounds apiece, despite GB outrebounding them 44-33.
Britain started slowly as the Belgians surprisingly started with a man-to-man defence, and with only a Durojaye basket to show for their efforts in the first four minutes, Belgium opened a 12-2 lead.
Barroilhet broke the run, but Belgium's lead grew to 15-4 before baskets from Stoddart and Barroilhet dragged GB back into the game, and three pointers from Stoddart and Yea cut the deficit to just 19-18 at the first break.
A pair of Yea free-throws gave Britain their first lead of the game with 45 seconds of the second period gone as GB started well with good play from Yea and Durojaye. That advantage grew to 26-19 at the midway stage of the quarter following a pair of Hannah Shaw baskets and one from Kelsey Bardsley.
Belgium replied with nine unanswered points before a pair of Dominique Allen free-throws sent the teams into the final two minutes of the half tied on 28.
Kim Snauweart gave Belgium the lead again, but a Durojaye basket followed by a single Barroilhet charity shot saw GB go into the locker room with a slender 31-30 lead.
The teams exchanged baskets in the early minutes of the second half, with a Durojaye jump shot keeping GB ahead by one with just under three minutes gone.
However, five straight Lien Lentacker point gave Belgium a 48-41 lead with four minutes of the period remaining, but baskets from Stoddart and Durojaye following by another late Yea score saw GB trail only 50-48 at the final break.
Allen levelled the score with a jump shot after 14 fourth period seconds, and a pair of Yea free-throws kept the teams level at the 7:31 mark.
Ippersiel gave Belgium a 59-56 lead just after the midway stage of the quarter, but four Durojaye points in a 6-0 GB run saw them take a 62-59 lead with 79 seconds remaining.
Strubbe hit a jumper to narrow the gap to 62-61 going into the final minute, but Yea doubled that advantage with a single free-throw.
A pair of Durojaye free-throws saw Britain's lead grow to 65-61 with 38 seconds remaining, but Metdagh drained a trey to cut the lead back to one with 23 seconds left.
Yea made it a two-point game with 12 seconds to go with a single free-throw, before Strubbe struck to seal an unlikely Belgium win.
