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.

It was mission accomplished for Sally Pearson on leg two of the Australian s bid to become only the second back-to-back winner of the event at the IAAF World Indoor Championships.

Ashton Eaton continues as the clear leader in the men s heptathlon and after a successful shot put, still has the world indoor record in his sights.

Jamaica s world indoor silver medallist Nesta Carter found his best form at exactly the right time and laid down a fine 6.50 season s best marker to confirm that he is intent on capturing the gold medal this time around.

Ashton Eaton is back in business. The US all-rounder had problems with his high jumping in Moscow at the 2013 World Championships because of a hamstring injury, but those problems are long gone.

Russia s Yekaterina Koneva won a modest contest with the shortest winning mark since the event was formally introduced onto the competition programme at the 1993 World Indoor Championships.