By Martyn Herman

RIO DE JANEIRO (Reuters) - Britain crushed the United States to win the women's track cycling pursuit title in another world record time as the two fastest teams locked horns at the Olympics on Saturday with the expected close battle ending in a romp.

After trailing early on, the quartet of Laura Trott, Katie Archibald, Elinor Barker and Joanna Rowsell-Shand cranked up the pace to devastating effect, winning in 4:10.236 -- nearly two seconds quicker than the world record they set in the heats.

Sarah Hammer's U.S. team, with unique left-sided drive chains on their bikes which are supposed to give them an edge, had thrown down the gauntlet with a world record in the morning heats, only to see Britain respond almost immediately in their heat.

It set up a mouth-watering prospect but the Americans, world champions in March, cracked and were no match for the rampant British in the final. Their wait for a gold in Olympic women's track cycling goes on.

Britain won by 2.218 seconds -- a country mile in the world of pursuiting -- to match the feat of the Bradley Wiggins-inspired men's team who won a much tighter duel with Australia to win gold on Friday, also in a world record time.

Trott, 24, is the first female British Olympian to win three gold medals and is only one behind the four of her fiance Jason Kenny who could take his tally to five in Sunday's sprint.

"We knew a world record was on the cards but it almost felt unreal," Trott told reporters.

"I actually said to Katie, 'that was possibly the easiest world record we've ever got'.

"I've never been in a team that feels so seamless. You can tell that everyone was giving 100 percent to get to the finish line first and I could not be prouder right now."

Incredibly, it was the fourth world record set in the women's team pursuit competition -- Britain lowering the mark by a full three seconds since action began on Thursday.

Canada secured only its second Olympic medal in women's track cycling, beating New Zealand for bronze.

The U.S. challenge was strong initially but when Kelly Catlin peeled off to leave Hammer with only Chloe Dygert and Jennifer Valente for company, the strain began to tell.

Especially as Britain, all four riders together, were working in perfect harmony with Trott setting a punishing tempo.

After streaking ahead, the last 1,500m were a formality.

"We were the underdogs, and that's what we are motivated on. We came close, we tried to push them but they were the better team for sure," Hammer, who will have to find a way to beat Trott in the omnium, told reporters.

Britain now has four medals in the track program which is only into its third day -- three of them gold.

(Editing by Ken Ferris and Ed Osmond)