NEW YORK, MAY 25 -- State Republican leaders have selected a wealthy but virtually unknown Manhattan economist to make what is widely viewed as a kamikaze run against Gov. Mario M. Cuomo (D) this fall.

Pierre Rinfret, 66, who lives on Fifth Avenue and heads an economic consulting firm here, is virtually certain to be nominated at the state GOP convention next week.

His selection ends an embarrassing, year-long search in which more than a dozen Republicans have passed up the chance to challenge Cuomo, who has raised $8 million and is highly rated in the polls despite the state's severe budget problems.

Rinfret, who has declined all requests for an interview, agreed to be drafted after discussions this week with state GOP Chairman J. Patrick Barrett and Manhattan Republican Chairman Roy M. Goodman. A spokeswoman at Rinfret Associates would say only that Rinfret "has expressed his interest in the possibility of becoming a candidate."

Goodman, a state senator, said Rinfret "is in the enviable position of being a brilliant underdog who may be able to pull off the greatest upset of the decade. He will be well-financed. He has indicated he will commit substantial personal resources to the race."

Barrett said today that the economist will focus his campaign on Cuomo administration policies "that are leading this state down the road to fiscal ruin."

Rinfret, an unpaid economic adviser to presidents John F. Kennedy, Lyndon B. Johnson and Richard M. Nixon, has never run for public office and is not even a registered Republican. Asked to describe the challenge that Rinfret would face, political consultant Jay Severin said: "Herculean."

Asked if he had ever heard of Rinfret, Cuomo's spokesman, Gary Fryer, said, "Nope." He declined further comment.

Cuomo is expected to announce his bid for a third term in a few days. The contest is likely to draw national attention because Cuomo is widely considered a possible Democratic presidential candidate in 1992.

New York state Republicans have been beset by fund-raising problems and were determined to find a deep-pockets nominee. Rinfret was chosen after financier John L. Loeb Jr., a former U.S. ambassador to Denmark, withdrew from consideration.