Catriona Matthew set her sights on becoming the first Scot to win the Women's British Open on Saturday when she eased into a three-shot lead with a third round 71 at Royal Lytham and St Annes.

Joint leader at halfway, 39-year-old Matthew, who has won six tournaments in her career, but never a major, had three birdies in the warm, breezy conditions and was one of only two players to make the clubhouse in sub-par figures.

She was on four under 212 with American Christina Kim, who also shot, 71 on one under.

But there are two big threats in joint a tie for third.

Ji-Yai Shin, the defending champion from South Korea, had a best of day 68, while Japan's Ai Miyazato, still basking in the glory of her breakthrough LPGA victory in the Evian Masters in France last week, carded a 70.

Matthew made a couple of early slips with bogeys at the third and fourth, but a 12-foot birdie putt at the short fifth got her back in the mood and she went on to add more birdies with a monster putt at the tenth and then from mid-range at the 13th.

"It's great to be in the lead, but there's still a lot of work to do," said Matthew, who is playing in only her second event since the birth of second daughter (Sophie) 11 weeks ago. She finished in the top 30 at Evian.

"I managed to stay patient today and tried to stay relaxed, although it was tough with the pressure," she said.

"The key here is to stay out of the bunkers and I pretty well managed to do that. My husband (Graeme) is my caddie and he also tries to keep me focussed. Tomorrow, I'll have to hang in and just try and keep it going."

Kim, who birdied the last from 12 feet, reckons Matthew will have an advantage.

"She's Scottish so she's used to these courses," suggested the 25-year-old Californian.

"But I just love links golf. This is my third time playing a British at Lytham and I just love coming over here. You have to stay patient, and that's what I tried to do today. It will be the same tomorrow.

Shin won at Sunningdale with an 18 under par total, and she has had to recover from an opening 77 to raise hopes of back-to-back victories.

"I'm right up there behind the leaders and this course is very tough, so I definitely have a chance," said Shin.

"It's much harder than Sunningdale. I got a lot of confidence winning last year and I feel I can play really well when it matters."