Katherine Hull is the best placed Australian after the opening round of the Safeway Classic in Oregon.

Hull made seven birdies in her round, but five dropped shots meant she had to settle for a two-under 70 and a share of 28th place.

American Sydnee Michaels and Japan's Mika Miyazato share the lead after the duo carded seven-under rounds of 65 to open up a one-shot advantage on three players in good scoring conditions at the Pumpkin Ridge Golf Club.

Both players picked up eight birdies and dropped just the one stroke during their rounds as 52 golfers ended the day under par.

Tied for third at six-under are Thailand's Pornanong Phatlum, Korean Inbee Park and American Cristie Kerr, while there is a group of four players a further stroke adrift at minus five.

World number one Yani Tseng struggled to make much impression on the greens and had to sign for a two-under 70, while her closest rival in the rankings - American Stacy Lewis - could only manage a 73.

Suzann Pettersen - who claimed the title with a marvellous 64 in the final round last year - made three birdies and two bogeys in a frustrating opening round of 71.

Veteran Australian Karrie Webb fired a level-par 72, while compatriots Sarah Jane Smith (73) and Lindsey Wright (75) struggled on the opening day.