A group of 60 business and opinion leaders from 18 Western Hemisphere nations yesterday denounced U.S. aid to rebels fighting the leftist government of Nicaragua but added that the continuing Latin American debt crisis is a bigger threat to regional stability than current fighting.

Sol M. Linowitz, who co-chairs the Inter-American Dialogue group, said members agreed that aid to the rebels, known as contras, "offers no solution to the security problems posed by Nicaragua and obstructs progress toward any regional peace settlement."

But Nicaragua should renounce support for rebels elsewhere in Central America and reduce its military ties to Cuba and the Soviet Union, Linowitz told reporters.

Elliot L. Richardson, former U.S. attorney general and defense secretary, said the group sees no problem with a Marxist state in Latin America in the context of a verifiable pact among all Latin nations renouncing support for subversion and civilian rebellions.

Former Ecuadoran president Galo Plaza, co-chairman of the private, nonpartisan organization, said the debt problem "is far more serious than anyone realizes in the United States, and nothing has been done to solve it."

He said a large-scale private investment plan proposed by Treasury Secretary James A. Baker III is "a step in the right direction . . . but inadequate."

In its third annual report on Latin troubles, the group proposed an economic revitalization program for the region that would include writing off part of some countries' debts and restructuring the rest. It would also require $20 billion in new capital and low-interest loans.