Sorenstam tied for lead

Annika Sorenstam enjoyed a strong start at the Sybase Classic on Thursday, firing a five-under-par 67 to join Song-Hee Kim and Rachel Hetherington at the top of the leaderboard after the opening round.

The former world number one, who announced on Tuesday that she would be retiring at the end of the season, made five birdies in a bogey-free round at Upper Montclair Country Club to continue her recent impressive form.

"Although I am going to retire at the end of the season, I still want to give my best every time I play. Today was very good," said the Swede, who has won her last two events.

Kim also enjoyed a bogey-free round while Hetherington had six birdies and a bogey.

World number one Lorena Ochoa is tied with five other golfers for fourth, just one shot off the lead, after carding five birdies and one bogey.

Ochoa has won the event in both of her previous appearances, taking the title at Wykagl in New York in 2006 before retaining it last year when it moved to Upper Montclair.

The Mexican won five of her first six tournaments this year before finishing fifth at the SemGroup Championship and tied for 12th at last weekend's Michelob Ultra Open.

Also on four under are Carolina Llano, Brittany Lang, Teresa Lu, Pat Hurst and Catriona Matthew.