The first-round lead was held on six under par by South Koreans Song-Hee Kim and Jiyai Shin in the Samsung World Championship at Torrey Pines.

In benign conditions, there were four birdies on the back nine for in-form Shin - while Kim set the pace with five birdies in her first eight holes.

The South Korean pair had just one stroke to spare on a field headed by Mexico's Lorena Ochoa and Sweden's Sophie Gustafson.

Paula Creamer, who won this tournament last year - when Kim was runner-up - finished day one three shots off the lead.

Kim had been expecting tougher conditions.

"Overall I think the greens were difficult to read out here today," she said.

"I expected the wind to play a major role but actually it wasn't so bad and it wasn't much of a factor."