Earlier this year, when Washington lobbyist I. Irving Davidson suspected that his indictment on political corruption charges was imminent, he told a reporter that he was "involved in some very sensitive stuff overseas . . . talking to people who our own people can't talk to."

Knocking Davidson "out of the box is going to hurt this country," he said in an interview in March. "I told those FBI people not to play superagent with me. . . .Look at my diary here: Jan 4, National Security Council. Do you think I planted that? I tell you that I'm dealing day and night with those boys."

Attempts at that time to get anyone in the White House or the Justice Department to talk about Davidson's alleged dealings with the NSC were unsuccessful.

Now it turns out that Davidson was indeed in touch with someone at the NSC in January in behalf of Oman, the strategic Persian Gulf kingdom that is so vital to U.S. global defense strategy.

On April 24, Davidson, who likes to refer to himself as "a door opener and an arranger," took an Omani expert on the NSC staff, Capt. Gary Sick, to lunch at the Gaslight Club on 19th Street with Dr. Omar Zawawi, brother of Omani foreign minister Qais Zawawi.

Once again, Davidson had been the middle man in a meeting from which everyone came away happy. Capt. Sick had gotten to meet one of Omani Sultan Qaboos' most influential advisers. And Dr. Zawawi had an important new Persian Gulf contact in the Carter White House, which had not been too friendly to him in the past.

Zawawi was pleased with the luncheon and apparently impressed with Davidson.

Two weeks later, representatives of one of Davidson's most important clients, Coca-Cola visited Oman to discuss doing buiness there. For Oman to do business with Coca-Cola would defy an Arab boycott that has kept the company out of most of the Middle East for more than a dozen years.

Alfred Friendly Jr., press spokesman for Brzezinski's staff at the NSC, confirmed yesterday that Capt. Sick had lunched with Dr. Zawawi and Davidson in April at the invitation of Davidson.

But Friendly denied that any business has been discussed in Capt. Sick's presence.

The discussion was entirely on the situation in Oman and U.S. and Omani relations' he said.

The Washington Post has seen copies of letters and telex messages in which arrangements were made for executives of Aqua-Chem, a subsidiary of Coca-Cola to vist Oman two weeks after the luncheon. Davidson had successfully helped negotiate a water desalinization project between Aqua-Chem and Dr. Zawawi's Omzest Corp.

According to the correspondence, R. N. Schantz, a vice president of Aquia-Chem, headed the delegation. Arrangements were made by Sam Ayoub, president of Coca-c0la's Middle Eastern operation.

The visit was cleared by Dr. Zawawi with the head of Oman's Israeli Boycott Committee.

Harvard-educated, Dr. Zawawi is a member of one of the wealthiest families in Oman. He owns homes in Washington and Flordia and on the West Coast. Allied in the past with at least one former CIA station chief in the Middle East, he has enjoyed close ties to both previous Republican administrations.

In February of this year, The Washington Post disclosed that Dr. Zawawi is one of the founders of a company here that calls itself "International Six Incorporated." His partners include Maj. Gen. Brent Scowcroft, who was Zbigniew Brzezinski's predecessor as National Security Adviser in the Ford Administration, and Col. John V. (Jack) Brennan, the trusted White House aide who resigned to follow President Nixon to San Clemente and most recently to New York.

According to one of the original incorporators of Isi, it was formed early in the Carter Administration. But Dr. Zawawi was not able to establish rapport with the Georgians. His one early meeting with Hamilton Jordon was described by an ISI source as "not a huge success."

Dr. Zawawi lost his most influentialcontact in the White House when Carter aides fired Warren L. (Bill) Gulley, who had been head of the Military Affairs office under three presidents. Gulley is now president of ISI.

The Carter Administration's ties to Coca-Cola are well-known and date back to the days when Jimmie Carter was governor of Georgia. Two of his closest advisers, former Attorney General Griffin Bell and personal confidante Charles Kirbo, are partners in the law firm of King and Spalding in Atlanta, which represents Coca-Cola.

Davidson, in an interview Tuesday, said that he was aware that Dr. Zawawi's overtures to Coca-Cola, which Davidson has represented as a consultant on and off since 1974, "could be interpreted" as an effort to disassociate himself with the Republican "outs" who run ISI for him and ingratiate himself with the Georgian "ins."

Davidson says that he made a pitch to Dr. Zawawi at the luncheon to "show your good faith" by cementing the Coke deal.

But Davidson maintains that Dr. Zawawi should be viewed "as a hero who is willing to take on the whole Arab world in behalf of his friends."

Davidson says that Dr. Zawawi told Aqua-Chem executives "they could bring a whole boatload of Coke with them when they came over. . . he didn't care what the Saudis said."

Of his own role in arranging the lunch as Dr. Zawawi's go-between with the NSC, Davidson says: "I ought to get a medal. . . we NEED Oman and they want us there.'

NSC spokesman Friendly says that Capt. Sick "had long wanted" to meet Dr. Zawawi, who is close adviser to Oman's Sultant Qaboos. Davidson had promised at a meeting "six months ago" to arrange an introduction the next time Dr. Zawawi was in Washington.

For more than 30 years, Irv Davidson has been one of the best-known behind-the-scenes promoters and lobbyists in Washington, representing, among others, the American interests of dictators in Nicaragua, Haiti and Cuba. He is registered lobbyist for Sudan. A target of the FBI's "Brilab" sting investigation, 'davidson was indicted on June 17 with reputed underworld boss Carlos Marcello by a federal grand jury in New Orleans, which accused them and others of fraud, conspiracy and racketeering.

Friendly said that neither he nor Capt. Sick was aware of Davidson's involvement in the FBI's "Brilab" sting investigation, although there has been extensive media coverage mentioning Davidson since February.

Friendly said that anyone making "any connection" between the luncheon and "the commercial dealings of any American corportation" would be very mistaken.

"I'm not aware of anything coming out of [the luncheon] except Dr. Zawawi giving Capt. Sick his telephone number," he said.

Spokesmen for Coca-Cola in Atlanta and Aqua-Chem in Milwaukee said yesterday that both Ayoub and Schanker were traveling and could not be reached for comment.