Career diplomat John E. Reinhardt, the first black America ambassador to Nigeria, will be named director of the United States Information Agency in the Carter administration, it was learned yesterday.

Reinhardt, 56, is assistant secretary of state for public and has been heavily involved in negotiations for majority rule in Rhodesia.

He will be the first career diplomat to direct the USIA, after a career that began with USIA, after a career that began with USIA in 1956 and continued until he became ambassador to Nigeria from 1971 to 1975. Reinhardt is the second black American, after Rep. Andrew Young (D-Ga.) ambassador-designate to the United Nations, to be named to a senior foreign policy post in the Carter administration.

By appointing a career diplomat to heard USIA, sources said, the new administration allows for more flexibility on any future reorganizations, notably the Voice of America.

Hundreds of VOA employees petitioned President-elect Jimmy Carter to create an independent broadcasting agency as an instrument of American policy. A panel headed by former CBS President Frank Stanton in 1975 recommended making VOA independent and in effect dismantling USIA by cultural functions conducted by USIA and the State Department.

The Carter administration wants more time to study these proposals, informed sources said.

Among appointments involving the State Department, Warrent M. Christopher, former deputy attorney general in the Johnson administration, has been selected as deputy to Secretary of State-designate Cyrus R. Vance, and Yale economist Richard N. Coper will become under secretary for economic affairs.

Vance and Treasury Secretary disignate W. Michael Blumenthal and competed for Cooper's services, with the decision going to State.

Vance met at the State Department yesterday with two other prospective appointees: Paul C. Warnke, former assistant secretary of defense, discribed as the favored candidate to head the Arms Control and Disarmament Agency, and Henry Owen, director of foreign policy studies at the Brooking Institution.

The Senate Foreign Relations Committee has scheduled an informal private meeting with Vance on Jan. 10, to be followed by a public hearing Jan. 11 on Vance's appointment and Secretary of State.

This technically will be an advance hearing on the appointment, following past practice, as Cabinet nominations officially cannot be made until Carter is sworn into office Jan. 20. Officially, the Senate committee will be hearing Vance so that it can report on his nomination as soon as it is received.