Top-seeded Stacey Martin had all the right moves yesterday, just as she has had all week.

A 17-year-old from Largo, Md., she defeated No. 2 Eleni Rossides, 6-1, 6-4, to win the women's singles title of the USTA National Amateur Championships at the Mount Vernon Health and Racquet Club.

The men's final will be played at 2 p.m. today. Top-seeded Arkie Engle, who defeated Scott Suhrer, 6-1, 6-2, yesterday, will meet Claes Ramel, who beat Carl Clark of Reston, 6-1, 7-6 (7-1).

Martin, who didn't lose a set the entire tournament, had a response for nearly every move Rossides tried, and breezed through the first set. But it was in the second set that Martin truly displayed her mettle.

Trailing by 3-0 and 40-30, she fought back for a service break that ended with Rossides double-faulting.

"That was the opening I needed to win," said Martin, who also won this tournament in 1984 and 1985. "Being down three-love isn't that bad, but to lose another game would have been disaster. It gave me a little more confidence because it showed a break in her concentration."

Martin won the next three games. And Rossides wasn't able to hold serve for the rest of the set.

"After losing that game {on the double fault}, I became defensive and began retreating," said Rossides, a graduate of Sidwell Friends in the District and now playing for top-ranked Stanford University. "And she began getting on top of the ball and that's what comes from being loose."

Rossides changed strategy and appeared to have Martin figured out when she opened the second set by slowing the pace with deep lobs. Rossides also tried to upset Martin's rhythm by taking the full 30 seconds allowed between points and 90 seconds between games.

"That almost killed me," said Martin. "If there's anything I hate, it's someone who takes that much time. I like a game to go fast and at first I had trouble adjusting to the change."

But after Rossides' double fault gave Martin the break in the fourth game, Martin overpowered Rossides with stunning backhands and cross court forehand winners.

"Unfortunately, I thought about that game too much," said Rossides. "I tried to tell myself not to, but it was too late."Women's Singles Final

Stacey Martin (1), Largo, def. Eleni Rossides (2), Washington, 6-1, 6-4. Men's Singles Semifinals

Arkie Engle (1), Brookline, Mass., def. Scott Suhrer (13), Jacksonville, 6-1, 6-2; Claes Ramel, Sweden, def. Carl Clark (16), Reston, 6-1, 7-6 (7-1). Men's Doubles Semifinals

Bill Benjis-Engle def. Jerry Frantz, La Grange, Ga.-Martin Persson, Sweden, 6-2, 6-1; Ken Anderson, Springfield-Clark def. Ian Skidmore, Lexington, Ky.-Sam Stinnett, Bessemer City, N.C., 6-3, 6-7 (9-7), 6-3.