Secretary of State Warren Christopher was having trouble last summer picking a new ambassador to Israel. He wanted someone the Israelis were comfortable with, someone they would see as expert in the peace process as well as someone with ready access to the highest administration officials.

He found what seemed the ideal fit: Martin Indyk.

Indyk was the National Security Council's senior director for Mideast matters, President Clinton's right-hand man for the region. An articulate Middle East expert and former head of a pro-Israel think tank, Indyk was highly regarded by Christopher and national security adviser Anthony Lake.

But if Indyk's nomination -- to be taken up today by the Senate Foreign Relations Committee -- now seems obvious, it is also unconventional. And his nomination shows how an itinerant college professor -- and an Australian to boot -- maneuvered through the think-tank world to the top of the U.S. diplomatic corps in a dozen years.

If confirmed, Indyk would be the first Jewish ambassador to Israel since the founding of the Jewish state, countering the long-held view at the State Department that sending a Jewish ambassador to Israel -- or a Greek to Greece or an Italian to Italy -- would inherently raise a conflict of interest.

Indyk also would likely be the newest U.S. citizen sent abroad to represent this country. Raised in Australia, he became a U.S. citizen in January 1993, little more than a week before Clinton appointed him to the NSC job.

In addition, he may be the first ambassador to have worked for another country's intelligence service. In 1978 he was for 10 months Australia's deputy director of current intelligence for the Middle East.

Also, the 43-year-old would be the first non-career ambassador to Israel since 1973. He neither crawled up State's steep career ladder nor did he buy the slot through political contributions. Rather, Indyk is a policy wonk whose lifelong "obsession" -- as he often puts it -- has been the Arab-Israeli conflict.

Despite his unusual background, Indyk has support throughout the foreign policy community. William Quandt, a former Carter White House aide who has often disagreed with Indyk, said he would make a good ambassador because "he's got good diplomatic skills and he's smart politically."

The Palestine Liberation Organization backs him. "His religion and background does not make any difference as far as we are concerned," said Hasan Abdel Rahman, the PLO's chief representative in Washington. "He understands the politics of the region . . . we can work with him. His commitment to Israel, with the right vision, may be even helpful to the peace process. Anybody who has the interests of Israel at heart and has a vision for the future will support an equitable peace with the Palestinians."

But Indyk is criticized by some as too tied to pro-Israel groups. Former U.S. ambassador to Israel William Harrop called the nomination "a profound mistake" and "bad for the Jewish community, bad for Israel, bad for the United States and bad for the peace process."

Quick Rise Indyk has credited his meteoric ascent to this country's willingness to welcome "anyone with a decent idea and a bit of energy and ambition."

Admirers cite his intellect, an entrepreneurial genius that attracted powerful political and financial backers, and his ingratiating charm and wit -- replete with a disarming grin that recalls British comedian Terry Thomas.

His critics call him "an operator" whose networking skills and political gamesmanship stand out in a town of gamesmen.

Indyk, who declined to be quoted for this article, has talked in the past to friends and reporters about why he emigrated to the United States.

He quit his Australian intelligence job, he has said, because he was frustrated by bureaucratic battles and by the lack of interest in the only region he cared about: the Middle East.

Indyk, who has a doctorate in international relations from Australian National University, dabbled in academia for three years only to find Australian students no more enthusiastic about the Mideast than the country's bureaucrats were.

Indyk took a six-month sabbatical at Columbia University in 1982. While in New York, an old friend invited him to Washington to help set up a research department for the powerful pro-Israel lobby, the American Israel Public Affairs Committee (AIPAC).

Within a year Indyk became frustrated anew: His research was not taken seriously because AIPAC was seen as an Israeli propaganda organ. At the same time, he felt that the traditional think tanks in Washington were too pro-Arab.

With the backing of an AIPAC board member and $100,000 in contributions, largely from the Jewish community, he became executive director of the Washington Institute for Near East Policy in early 1985. Moving Away From AIPAC

This was never going to be just another academic study group.

"We were very driven with this sense that we were not just around spinning ideas," an early participant said. It was clear "that we were really trying to influence policy. We focused narrowly on the Washington policymaking community, and we were going to try to influence them and to educate them. We felt that the {U.S.} policy at that time was based on false assumptions and that we should try to change that" to a more pro-Israel view, the participant said.

But Indyk understood that it was critical for the new institute to distance itself from AIPAC if it was to have any credibility. Arab views had to be aired and published, as did a range of Israeli views. Anyone labeling the institute as part of, or a spinoff of, AIPAC or even as "pro-Israel" was admonished that it was independent and "pro-American."

Critics ruefully acknowledge Indyk's success in repositioning himself and the institute.

James Zogby, executive director of the Arab American Institute here, said, "What they were able to do was define their pro-Israel leaning into invisibility, and they challenged indignantly anyone who said otherwise. And it worked."

"Indyk did a great job at turning it into a very serious and credible organization," said Quandt. "It was originally thought to be the arm of {AIPAC}, and it seemed that way at first," but Indyk steered it to a more independent approach, he said.

The institute's budget rose quickly to more than $1 million and it employed 10 full-time staffers. It became the center of the debate on the Middle East, crowding out more traditional think tanks.

Former vice president Walter F. Mondale, former secretaries of state George P. Shultz and Alexander M. Haig Jr., former U.N. ambassador Jeane J. Kirkpatrick and other luminaries joined its advisory board. Khalil Jahshan, head of the National Association of Arab Americans, said, "It is the most dramatic success story in lobbying and influencing decision-making I've seen in this town in the 20 years I've been here." Adviser at the Top In 1988, Indyk was part of a trio of Jewish leaders who briefed presidential candidate and then-Massachusetts Gov. Michael S. Dukakis on Mideast issues.

In early 1989, Secretary of State James A. Baker III laid out U.S. policy for the region in a speech that closely tracked a 1988 institute study urging a gradual, slow approach to the peace process and reciprocal "confidence-building" steps by Israel and the Palestinians. Six of the experts who worked on the institute's report landed top policymaking positions in the Bush administration.

Indyk briefed then-President George Bush on the Middle East in 1989, invited by Dennis Ross, who knew Indyk when both were at AIPAC. Ross was head of policy planning at the State Department for Bush and is now point man there for Mideast policy.

By the 1992 presidential campaign, Indyk and the institute were briefing Democrats and Republicans alike.

But Indyk's effort for Clinton was more pronounced. Indyk first briefed the president in September 1991, before he announced his candidacy. Indyk briefed him three times after that and wrote a policy paper for the transition team.

Indyk's view, based on his writings and speeches then, was to continue the Bush approach. But he also felt that the end of the Cold War, Iraq's defeat in the Gulf War and the election of a Labor government in Israel gave Clinton a golden opportunity to move the peace process forward.

Indyk "told Clinton he could obtain four treaties by the time he finished his first term," said a source who attended the briefings: one with Israel and the PLO, another with Jordan, a third with Lebanon and a fourth with Syria.

"That is something that I want to do," the source said Clinton responded.

When NSC director Lake offered Indyk the White House job in mid-December 1992, there was one hitch: He was not a U.S. citizen. Indyk, who obtained a green card in 1987, applied for citizenship in mid-1992, sources said, shortly after he completed the required five years as a permanent resident.

He took the citizenship examination at the Immigration and Naturalization Service office in Arlington that fall -- missing a question about the number of members of Congress -- and was sworn in at a group ceremony at federal court here on Jan. 12, 1993.

Ten days later he was on the job. Arab Americans protested his appointment. "To choose a person with a highly partisan background to be the gatekeeper on Mideast issues, controlling the information traffic to the president's desk, was unwise," Jahshan said. He said, however, that he would not oppose Indyk's nomination.

But former senator James Abourezk (D-S.D.), national chairman of the American-Arab Anti-Discrimination Committee, objects, although, he said, "he'll do less damage to America there than in the White House."

And Harrop said that while it may be time to break the tradition of not having a Jew as U.S. ambassador to Israel, it was wrong to submit for the job a former AIPAC employee who was "so strongly associated with Israel." Indyk's "been an American" only two years, Harrop said.

Indyk's supporters say his background will enable him to speak frankly to Israeli leaders. Another former U.S. ambassador to Israel, Samuel W. Lewis, agrees. "I can't think of anyone who would be a better choice," Lewis said, adding that Indyk has "credibility with the Arab governments." And, Lewis said, he has "been a central player and knows all the actors well and can hit the ground running in a way no one I know could do." Staff researcher Barbara J. Saffir contributed to this report. CAPTION: MARTIN INDYK