Jam sessions and jambalaya will be the featured attractions Sunday, June 18 at Washington's hottest new entertainment spot, the South Lawn of the White House.

That urban green pasture, where a few days ago the New York City Ballet performed for NATO dignitaries, will be the scene of a jazz festival featuring performances by more than 50 of America's leading artists. There have been many concerts at the White House before, including some jazz concerts, but nothing comparable in scope to the event which is being billed as the White House Jazz Festival.

The event was planned to salute the 25th anniversary of the Newport Jazz Festival and, according to the White House press release, to "pay tribute to a unique American art form."

In an hour and a half, the minifestival will present the most impressive array of jazz talent ever assembled in one place to perform in a single concert. The list of performers reads like a combined history and hall of fame for the art that is America's most distinctive contribution to the music of the world.

A few names indicate the concert's enormous range, from such venerated old-timers as Eubie Balke, Earl "Fatha" Hines, Dizzie Gillespie, Lionel Hampton and Illinois Jacquet to younger performers like Herbie Hancock and Chick Corea; from masters of the intricate, abstract arabesque such as Cecil Taylor to pop artists like George Benson who number their fans in the millions.

Before the concert which is scheduled to begin at 6:30, 600 guests will be served a buffet luncheon on the lawn, prepared by the Jambalaya Festival Association of Gonzales, La. The meal will be cooked in four large, open pots over open fire out on the lawn, according to Paul Leblanc of the Jambalaya Association.

The White House event will fall neatly between two uniquely American festivals and blend the highly compatible flavors of both. The Jambalaya Festival (now in its 11th year) takes place in Louisiana on the week-end of June 10-11; the Newport Jazz Festival will be held in New York from June 25 to July 2.

Two kinds of jambalaya will be served: pork and sausage and chicken and sausage. All the ingredients will be brought up from Louisiana, as will be 75 bushels of pecans to be used in preparing fresh, homemade pecan pie.

"To cook that much jambalaya takes approximately four to six hours," Leblanc said so the show on the South Lawn should be under way by noon.

Guests will include jazz performers, composers, scholars, critics, and representatives of the music industry and of Jazz organizations.

Other performers include Katherine Handy Lewis, Dick Hyman, Doc Cheatham, Teddy Wilson, Buddy Rich, Ray Brown, Roy Eldridge, Stan Getz, Charles Mingus, Matthew Houston, Herman Sherman, Joshua "Jack" Wilis, Walter Payton Jr., Lester Caliste Jr., Joseph Torregano, Lawrence Trotter, Ernest Watson, John Simmons, Gregory Stafford, Charles Barbarin Jr. and Clark Terry.

Also Dexter Gordon, Seny Rollins, McCoy Ty ner, Tony Wiiams, Ron Carter, Mary Lou Wilams, Max Roach, Stanley Clarke, Ilt Hinton, Zoot Sims, Benny Carter, Gil Evans, Gerry Mulligan, Ornett Coleman, Billy Taylor, Mercer Elligton, John Lewis, Sam Rivers, Geoge Russell, Joe Newman and the Yong Tuxedo Brass Band.

Harold Boxer, music director of the Voice of America, said the overseas radio network will provide immediate reportage on the event and will record the concert for late broadcast throughout the world. Nathal Public Radio will preempt part ofts evening news programming for a broadcast of the event, beginning at 6 p.m. will Billy Taylor (who will also perform) conducting live interviews from the White House lawn.

The program is scheduled to end at 8, but a glance at the array of performers indicates that once begun, they may still be jamming at midnight.