The Greeks and the Turks, who have been fighting each other off and on for centuries in the Mediterranean, called time out over a few drinks in Washington last night. Greek Ambassador Menelas Alexandrakis wandered across the street to the Turkish Embassy where Ambassador Melih Esenbel was saying farewell at a reception.

"We have to cooperate," said Alexandrakis. "We're looking forward to better times. Our future lies in working together."

Alexandrakis and his wife did not stay long but some guests were startled that they showed up at all.

"I was surprised," said Esther Coopersmith, veteran observer of foreign policy - at least as it occurs at embassy parties. "But people who disagree can be friendly anyway."

Esenbel, who said he and his wife had invited "400 to 500 of our closest friends," returns to Turkey in a few days, ending a 42-year diplomatic career that was interrupted a few years ago when he was called home to serve as prime minister. He returned to Washington at the height of the U.S. arms embargo against Turkey.

"He did what he set out to do, he got the arms embargo lifted," said public relations executive Bob Gray. "Turkey's interests here are in good shape thanks to him."

But Esenbel admitted that times have been better between the U.S. and Turkey, especially now that his government is under pressure here to permit U2 spy planes over his country. The Carter administration considers the issue important in winning votes for SALT II.

"If U2 flights over Turkey are necessary to replace bases that we had in Iran, I would hope they would be approved by the government of Turkey," said Sen. Charles Percy (R-Ill.), a member of the foreign relations committee.

Percy arrived at the reception sporting a sunburned nose, caused, he said, by marching in four Fourth of July parades. "The first one was down Michigan Avenue in Chicago with Muhammad Ali. Believe it or not, I asked him if he had taken a position on SALT. He said he didn't know much about it yet, so I told him I'd send him some material. I think 'The Greatest' should be informed on everything."

The Esenbels' drawing power attracted a large turnout that included several ambassadors; Sens. Richard Stone (D-Fla.), John Tower (R-Tex.) and Edward Zorinsky (D-Neb.); assistant secretaries of State George S. Vest (European affairs) and Hodding Carter III (public affairs); former Senators Huugh Scott and John Sherman Cooper, and two members of Jimmy Carter's cabinet.

Both Interior's Cecil Andrus and Justice Department's Griffin Bell claimed they knew nothing about what's been going on at Camp David.

"All I do is run the Justice Department," said Bell.

"I haven't been asked to go," said Andrus, who insisted he didn't feel left out. "The president and I have a good enough relationship that he knows I'm as close as the phone."

Others among the guest included:

Nicaraguan Ambassador Guillermo Sevilla-Sacasa, claiming things were just fine in civil war-torn Nicaragua and that his in-law, President Somoza, "is a great president - don't believe everything you read";

Mrs. Warren Burger, complaining of the heat and refusing to reveal details of her husband's trip to New York. "I'm a mum woman - I can't tell anybody anything but you'll see it in the newspapers.";

And White House curator Clement Conver, telling about the four Turkish Hereke rugs in the White House. "Ofcourse, they could give us another one anytime they want to." CAPTION: Picture, Turkish Ambassador and Mrs. Esenbel with Portuguese Ambassador Joao Hall Themido, right; by Lucian Perkins