The Sans Souci, a Washington restaurant of the politically and socially elite, settled a nearly two-year union strike late Monday night. Much to columnist Art Buchwald's delight.

"This is bigger than Carter going to the Middle East, I might go there again," said Buchwald, once a regular Sans Souci customer, minutes before he was to deliver a speech before a gathering of the United Jewish Appeal in New York City last night.

Pierre Sosnitsky, maitre d'hotel and manager of the restaurant, said simply, "I'm extremely happy that the strike has ended. What has happened is extremely positive. The strike has definitely hurt the business, but it's too early to tell how much."

According to Sosnitsky and a union spokesman, the owner, Bernard Gorland, has agreed to new employe benefits that include paying Blue Cross and Blue Shield contributions for employes, paying for full family dental care and later full family legan care, sick leave, holidays with pay and a new employe grievance procedure. Gorland could not be reached for commment.

Ron Richardson, executive secretary treasurer of the Hotel and Restaurant Employes Union local 25, the union representing Sans Souci employes, said union officials met yesterday with the restaurant's 30 employes to explain the new benefits.

But the meeting in the dining room was delayed temporarily while employes and union officials waited for TV producer Norman Lear to finish lunching on Bon Valet with Bearnaise sauce and cordon of tomato. ("Everybody else in town calls it Eggs Benedict, but we have to be different," said Sosnitsky.