Amateur Wayne DeFrancesco of Reston pushed aside the pros yesterday at Army Navy Country Club in Arlington and led four qualifiers into the U.S. Open golf championship.

The slender 23-year-old former Louisiana State player shot three-under-par 69 in his afternoon round and finished with a 36-hole total of 141 strokes to gain the Open, to be held for the fourth time at Merion in Ardmore, Pa., June 18-21.

Another amateur, former University of Maryland player Mark Lawrence of Richmond, was next at 73-70 -- 143, with 12 birdies in 36 holes. Pro Al Green of Crownsville, Md., scored a triple-bogey 7 on the 14th hole after a morning delay caused by an electrical storm, but still qualified with 73-71 -- 144.

Lee Lder of Langston, who led after a morning round of 69 but ballooned to 77 in the afternoon, won a four-man playoff with a birdie on the first extra hole. The other three players in the playoff at 146 were amateur Greg Carpousis of the host club (71-75) Tom Hanna of State College, Pa., (76-70) and Mark Alwin of Woodholme (74-72).

DeFrancesco's putting improved when the winds picked up in the afternoon and he birdied six holes. He said that a bogey at No. 14 -- where he visited water and sand before salvaging a 5 with a 15-foot putt -- was important. He then birdied the next two holes.

Elder, 46, who won $15,600 by tying for third in the Atlanta Classic over the weekend, apppeared to tire on his final 18 holes.