Japan's Mamiko Higa birdied her final hole in fading light to maintain her lead at the US Women's Open where the second round was delayed for two hours due to thunderstorms and then suspended because of darkness.

The winner of this week's US Women's Open will receive a record $1 million as part of a boost in prize money that will also see next month's US Open solidify its status as golf's richest major, organisers said Tuesday.