England's Georgia Hall is seven off the lead after a one-over 73 second round.

Play was delayed by rain for two hours, and 31 players were unable to finish the round before darkness fell at The Club at Carlton Woods in Texas.

Peiyun Chien, who emerged as a surprise leader in the opening round, sits on five-under with four holes left.

Vu was alone at the top of the leaderboard for much of the day with a midway total of seven-under 137, before Kim returned eight birdies after a bogey on her opening hole.

Olympic champion Nelly Korda is tied for fourth after another mixed round, carding three bogeys and five birdies.

"There are bogeys out there and you try to minimise your mistakes as much as possible," said Korda.

"I was punching the air a couple of times after my two three-putts, which are kind of stupid mistakes, but you just kind of have to stay mentally tough and know that there are some birdie opportunities as well."

World number one Lydia Ko, who was on three-over with two holes to complete when play was halted, is likely to miss the projected one-over cut.

Jennifer Kupcho's hopes of defending her title are slim, with the American also set to miss the cut after a six-over 78 that included a triple-bogey, double-bogey and three bogeys against two birdies.