Great Britain produced their best defensive effort of the summer to beat Belarus 83-51 in Minsk and qualify for the play-offs in Europe's Division B.
Deng was an inspirational presence for Great Britain
Luol Deng had 27 points and Andrew Betts added 12 as GB shut down their hosts in the second half of the game.
Belarus threatened to win at the start of the second half when they reduced the arrears to 40-35.
But Deng inspired an immediate 18-5 run and Belarus were allowed only 16 points in the remaining 18 minutes.
Both teams went into the game needing a win to advance towards the qualifying matches for the 2009 European Championships.
Great Britain will now face a two-leg tie on 11 and 15 September against Finland, Georgia, Switzerland or Romania - depending on results in other groups.
It was Great Britain's stout defence that saw them through in the end.
The effort was phenomenal - it just feels like every time this team steps out there it gets better
Deng had nine points in that 18-5 run and his defensive intuition in the fourth quarter saw him snare a pair of steals and start an 8-0 run that made sure of victory.
British coach Chris Finch hailed Deng's contribution, saying: "He makes plays out of nothing - he makes steals, he's always in the right spot.
"He was definitely up for the game, he was very aggressive considering he got two early fouls.
"We told him they would mark him and try to come after him and intimidate him early on."
Captain Andrew Sullivan, who scored 11 points, never felt the result was in doubt. "I expected us to win because we didn?t have any choice," he said.
"To win by 30 was a surprise for all of us. The effort out there was phenomenal. It just feels like every time this team steps out there it gets better."
British Olympic Association chief executive Simon Clegg was proud of Great Britain's achievement.
"Having lost by a solitary point at home to Belarus last September the pressure was really on," said Clegg.
"The team have clearly handled that pressure exceptionally well and I am sure this will be seen as a pivotal moment on the long road to gaining entry to the London 2012 Olympics."