The United States obliterated one of track and field's longest-standing world records and raced past China on the medals table at the London Olympics on Friday.

The American women's 4x100m relay team clocked 40.82 seconds, bettering East Germany's previous world best of 41.37s set in Canberra in 1985.

But America's reign in the men's 4x400m relay was ended by the Bahamas - the first time since 1984 the US haven't won Olympic gold in the event.

With two days remaining of the London Games, the US climbed to the top of both the gold medal and overall medal tables.

The Americans have collected 41 golds, 26 silver and 27 bronze, ahead of China's 37 gold, 25 silver and 19 bronze.

Host Great Britain remain third with 25 gold, 15 silver and 17 bronze.

America's stunning women's relay win featured 200m gold medallist Allyson Felix, reigning 100m world champion Carmelita Jeter, Tianna Madison and Bianca Knight.

"I knew that these girls were going to run their hearts out," said Jeter.

"I knew we were running fast. I was already pointing at the clock, saying 'there it is'.

"There was a cloud hanging over us, with people saying 'they can't do this, they're going to drop the stick' but we did it."

Ethiopian Meseret Defar claimed consecutive women's 5000m Olympic titles by beating compatriot Tirunesh Dibaba while Turkey's Asli Cakir Alptekin won the women's 1500m.

Frenchman Renaud Lavillenie took gold in the men's pole vault with a best clearance of 5.97m as Australia's defending champion Steve Hooker failed to clear a height.

The US's table-topping day was helped by their wrestling poster boy Jordan Burroughs winning the 74kg freestyle category - he has now won 38 consecutive bouts.

The Americans have already inked at least one more gold after their men's basketball Dream Team demolished Argentina 109-83 in a semi-final to set up a Sunday final against Spain.

And the Netherlands retained their women's Olympic hockey title with a 2-0 defeat of Argentina.

Winners of all seven of their games, the Dutch women gave their male compatriots extra incentive to record the first ever Olympic hockey double when they meet Germany in the gold medal match on Saturday.

At Serpentine Lake in London's Hyde Park, Ous Mellouli won the 10km open water swimming race.

The Tunisian's gold came less than a week after taking bronze in the 1500m freestyle at the Aquatic Centre pool - the first swimmer to win outdoor and indoor swim medals at the same Olympics.

NZ Newswire