LOS ANGELES (AFP) - World No. 2 Ko Jin-young will have to wait to try to build on her lead at the LPGA Portland Classic, where an overnight downpour forced play to be cancelled on Saturday (Sept 18).

The LPGA said in a statement that course conditions were affected in the morning, after Oregon Golf Club received about 4cm of rain overnight, coupled with a forecast for further rain, prompting officials to pull the plug on the day.

"Tournament officials will continue to monitor the rainfall and assess the golf course in anticipation of beginning the third round on Sunday," the Tour said in a statement.

Officials decided on Saturday night to trim the tournament to a 54-hole event.

Donna Mummert, the LPGA's senior manager of rules and competition, told Golf Channel that when officials assessed the course at daybreak they found bunkers as well as several greens and fairways underwater.

With rain still falling in the afternoon, she said, there was no time for the course to drain and allow grounds staff to make repairs.

"We need more drying time and we're just not going to have that today," she said. "We just don't have the playable conditions that we need in order to conduct a competition round today."

South Korea's Ko surged up the leaderboard on Friday with a five-under 67 that gave her a one-shot lead through 36 holes.

Ko, playing in her first tournament since failing to win a medal at the Tokyo Olympics, made six birdies on Friday with just one bogey.

Scotland's Gemma Dryburgh was one shot behind Ko after firing a second-round 69.

First-round co-leader Carlota Ciganda of Spain was in solo third, three shots off the lead.