Sorenstam, the Swedish veteran, had a much better day on Friday after shooting 71 in the opening round, soaring up the leaderboard with four birdies in her final four holes.

A second-round 67 keeps the Swede in touch with Ochoa, but catching the in-form Mexican, who won eight times on the LPGA last year and has only missed four cuts in five years on tour, will be a tough task over the final two rounds.

Number one motivation

Sorenstam, looking for her 71st career title, is desperate to wrest back her number one ranking that Ochoa took from her during an injury-plagued 2007, and is using that as motivation for this season.

"Anything can happen," Sorenstam said.

"It's a great course and I've just got to make some more birdies like I did at the end here and make some low scores which I can do.

"It's always nice to get a good round to get the momentum going.  There's no doubt Lorena is playing well so I've got to do the same again to catch up."

Karrie Webb, Australian former world number one, American Stacy Prammanasudh and Sweden's Linda Wessberg sit one shot further back on five-under 139 after two rounds.

The Women's Champions tournament, played at Tanah Merah Country Club, is the biggest and richest women's event staged in the region, with $2 million in prize money up for grabs.

Only winners on the LPGA Tour, and champions from the Ladies European Tour and tours in Japan, Korea, Australasia and Asia, are eligible to play.