The US quartet improved the world lead by more than a second in speeding to 3:29.06 to establish themselves as the favourite for the gold medal in Sunday’s final.
Natasha Hastings, a regular member of successful US relay teams in recent years, opened their campaign and the squad took the second heat with reasonable ease as Jernail Hayes took over in the lead on the second leg and the USA were never headed.
Monica Hargrove then passed the baton on to 2012 NCAA 400m hurdles champion Cassandra Tate. Jamaica came through strongly to clock a 3:29.43 national record.
Behind them, Poland registered a 3:29.48 season’s best and the Nigerians clocked a 3:29.67 personal best.
Utilising world 400m champion Christine Ohuruogu on their anchor leg, the British team claimed the first heat with a 3:30.60 season’s best, while Russia – the eight-time champions of this event – ran a 3:30.60 season’s best for second place behind them.
Although failing to qualify for the final, Italy set a 3:31.99 national record when finishing in third place in heat one.
Nicola Bamford for the IAAF