Los Angeles (AFP) - Women's world No.1 Lydia Ko and world No. 2 Ariya Jutanugarn pace an elite field for this week's LPGA Kia Classic, the last tune up for next week's first Major championship.

In all, 23 of the world's 25 top-ranked players will compete at Aviara Golf Club near San Diego ahead of next week's ANA Inspiration at Rancho Mirage, California.

But 19-year-old Ko will be a focus as the reigning champion at both the Kia Classic and at Rancho Mirage even as she tries to enjoy some of her favourite holes.

"This is my favourite stretch of events," Ko said. "I don't think it really clicked until I had to do media days that I actually did win back to back. They are great events."

Many players, including South Korea's sixth-ranked Jang Ha Na, will try to treat the week like any other even as she fine tunes her game in quest of a first Major title next week.

"It feels really good this week. So maybe it will be a really good score after this week," Jang said. "Feels really exciting, but not thinking too much, not thinking too differently. Just thinking tournament."

Thailand's Ariya has been ranked second to Ko for the past 34 weeks and hopes to close the gap even as the South Korean-born Kiwi has found her form with three top-10 showings this year, including shares of eight last week at the Founders Cup and in Thailand as well as ninth at the HSBC Women's Champions in Singapore.

But Ko has yet to win since making wholesale changes in her support team before the start of the 2017 campaign, using a new swing, caddie and coach.

Ko and Lizette Salas each fired four rounds last week without a bogey, a feat achieved by only two other players since 2011.