
Trevor Stewart, Randolph Ross, Bryce Deadmon and Vernon Norwood were quick off the block and came into the first changeover second but then took a lead they never relinquished as smooth changeovers took them to a time of 2:57.77s.
Botswana finished second ahead of Trinidad and Tobago, and showed that they could be a real threat for a podium finish at the weekend.
In the second heat, Poland, who have already won gold the inaugural Olympic 4x400m mixed relay, produced a brilliant come-from-behind win in a season’s best time of 2:58.55s.
Also through to the medal round are Jamaica, who also clocked a season’s best of 2:59.29s to finish second.
Belgium’s third-place performance was also enough for them to advance.