USA recorded a time of four minutes 12:282 seconds, only for GB to then clock four minutes 12.152 seconds to reclaim the world record.
Sarah Storey takes record 12th gold Paralympic medal
The two teams will go head-to-head in the final this evening (20:53 BST) in what promises to be a cracker as GB look to add to Saturday’s gold medal haul.
The quartet of Laura Trott, Joanna Rowsell-Shand, Elinor Barker and Katie Archibald overwhelmed Canada in the heats to reach the final.
Racing in their heat against Australia, the world champion Americans, led by Sarah Hammer, broke the record set by Britain in Thursday's qualifiers by a full second.
Expect the world record to be broken once more this evening, but which team will do so remains to be seen.
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