Defending champion Karen Jones of Argyle sank a six-foot birdie putt on the 19th hole and beat Kim Williams of Bethesda yesterday in the semifinals of the Maryland State Golf Association Women's Amateur tournament at Bretton Woods.

Jones, 20, will play Cindy Davis of Crofton for the title today. The match will start at 9:28 a.m.

Davis, 20, this tournament's medalist and the Middle Atlantic Golf Association champion who plays for Furman University, birdied three of her first seven holes for a 4-up lead and eliminated 1979 champion Patty Thompson of Cumberland Country Club, 2 and 1, in the other semifinal.

For the 37 holes she needed to win two matches today, Jones was one under par in the 95-degree heat.

"I'm not that tired, just mentally exhausted," said Jones, who plays No. 3 on Oklahoma State's women's team. She finished 24th in the NCAA women's tournament this spring. "These young girls were trying to beat up on me today."

Jones parred the 18th hole in her morning quarterfinal for a 2-up victory over Clare Dolan, 15, of Montgomery Village.

In the afternoon, Williams, 19, birdied the third hole to go 1 up, then hit a magnificent long-iron second shot that stopped a foot from the cup at the par-4 fifth. That birdie gave Williams, a finalist in the women's district championship, a two-hole lead.

Jones appeared calm, however, and pulled even at the par-3 ninth when Williams three-putted.

Jones took the lead at the par-3 14th hole with par after Williams' tee shot stopped short of the green, she chipped up and missed a nine-foot putt.

Williams won the par-5 15th with a four-foot birdie putt and, after halving the next two holes, they came to the uphill par-5 18th tied.

Both Jones and Williams were just off the green in two shots. Jones chipped to five feet and Williams to eight feet. Both made their birdie putts to force the match to the first extra hole, a par-4.

Both hit good drives, Jones wedged to six feet and Williams to 17. After Williams missed her birdie putt, Jones curled in hers to win the match.

In morning quarterfinals, Williams beat Sarah LeBrun of Green Spring, 2 and 1; power-hitter Thompson defeated Jane Abood of Kenwood on the 19th hole when Abood hit her approach shot over the green; and Davis beat Michelle Mackall of Washingtonian, 5 and 4. Davis was one under par in her two matches.