Two Nobel Prize-winning economists said yesterday that U.S. Roman Catholic bishops were hardly naive or foolish, as critics have suggested, in drafting an economic statement calling for a major national commitment to reducing unemployment to 4 percent or even lower.

"Four percent is not unrealistic with a concerted effort" toward education, training and federal job programs as well as changes in government financial policies, said Prof. James Tobin of Yale University, winner of the Nobel Prize for economics in 1981.

Prof. Lawrence Klein of the University of Pennsylvania, the 1980 Nobel laureate in economics, said spending cuts and tax increases could reduce the federal budget deficit by about $100 billion by the end of the decade. This, he said, would allow creation of more money by the Federal Reserve Board, reduce the value of the dollar and bring unemployment down to 5.6 percent from the current 7.3 percent. Declines below that rate could be won at the expense of higher inflation or, preferably, through job-creation and training programs such as those suggested by the bishops, Klein said.

The National Conference of Catholic Bishops issued the first draft of a major teaching statement on the U.S. economy last November. The document, which will be revised before final approval next November, calls in general for the government and for individual Americans to take the poor and the economically powerless into greater account when making economic decisions.