Americans Boo Weekley and Heath Slocum hit a solid three-under-par 69 to retain a one-shot lead over their more fancied rivals after the second-round foursomes at the World Cup today.

Ireland duo Michael Hoey and Gareth Maybin remain at six under par, eight off the lead, after shooting level par on day two.

Pre-tournament favourites England raced off and topped the leaderboard by two shots midway through the round, but the whole field found the alternate ball format more taxing and a late bogey dragged them back down.

Weekley and Slocum also had a bogey either side of the turn but picked up five birdies to move to 14-under for the tournament with England and Scotland tied for second a shot back.

"It's a difficult format," Slocum told reporters.

"We would have liked to have shot something lower but we started the day ahead and we we finished it ahead so we're in good shape going into tomorrow."

England's Justin Rose and Ian Poulter looked set for a good score at five-under through 10 holes but they parred the next five and dropped a shot when Poulter sent the ball racing past the 17th hole to leave his partner with a seven-foot par putt.

"It's a little bit of a shame when you've got off to such a flying start," said Poulter after a four-under 68.

"The only really disappointing thing was the first putt on the 17th. But we certainly go into tomorrow feeling good."

Scotland also looked like dropping a shot at the penultimate hole after Marc Warren's tee shot landed down a hill some 50 feet from the hole but Colin Montgomerie chipped the ball beautifully to leave the younger man with an easy par putt.

Warren made amends at the 18th with an approach shot to five feet that Montgomerie drained to give last year's runners-up a 68.

"I think six birdies in a tough format like that around this golf course, it's a positive," said Warren.

"We've come out of that and we're right in contention," added Montgomery.

South Africa looked like taking a share of second when Retief Goosen nailed a 20-foot putt for birdie at the 17th but the former US Open champion found the rough with his drive at the 18th and a fourth bogey of the day dropped them to 69.

That left Goosen and Trevor Immelman alone in fourth place on 12-under for the first two rounds, a shot ahead of defending champions Germany, Italy and Denmark.

The format switches to fourballs again on Saturday and then back to foursomes on the final day of this $5 million tournament.