By Martyn Herman
RIO DE JANEIRO (Reuters) - The battle on the boards between Britain and the United States for Olympic women's team pursuit gold sizzled on Saturday as the two favourites traded world records in quick succession.
Sarah Hammer's American outfit threw down the gauntlet with a superb ride in their heat against Australia, clocking four minutes 12.282 seconds for the 4,000m endurance event -- a second quicker than Britain's time in Thursday's qualifiers which itself was a world record.
The morning crowd in the Rio velodrome was still abuzz when the British quartet set off in the final first-round heat against Canada and went even quicker than the Americans, stopping the clock at 4:12.152.
Gold will be decided later on Saturday when the two teams clash in a mouth-watering showdown between the British reigning Olympic champions and the world champions.
Veteran Hammer is hoping to lead the Americans to a first gold medal in Olympic track cycling.
The brand new Olympic velodrome has already witnessed six world record rides, including two by the British team pursuit squad led by Bradley Wiggins who beat Australia to gold in an epic duel on Friday.
China also lowered the world record on the way to winning the women's team sprint.
Canada and New Zealand will race for bronze.