Government officials pay courtesy calls on the pope in Rome in his capacity as a head of state, not a religious leader, according to officials of the State and Defense departments.

They made the point in letters to Nicholas Royce, a Greek Orthodox layman in North Hollywood, Calif., who has carried on a "one-man crusade" to give Orthodoxy more public recognition in the United States, particularly in situations where religious leaders are represented at public events.

Royce wrote to the State and Defense departments to complain that neither Secretary of State George P. Shultz nor Defense Secretary Caspar W. Weinberger called on Ecumenical Patriarch Dimitrios I, the "first among equals" of world Orthodoxy, when they were in Istanbul recently.

"If U.S. government officials can take the time to visit the pope of Rome, I feel the same courtesy could have been extended to the ecumenical patriarch," Royce said.

George B. High, senior deputy assistant secretary for public affairs of the State Department, wrote in response that "unlike other spiritual leaders, the pope is also the head of state of the Vatican proper . . . . For this reason, the U.S. government has separate diplomatic relations with the Vatican, and the president appoints a representative of this government to serve as ambassador to the Holy See."