The Peace Corps director is urging American cities to use more of the 120,000 veterans of his volunteer agency to do the same job many of them did in the Third World: teach disadvantaged youngsters.

Paul D. Coverdell told the U.S. Conference of Mayors on Thursday that more than 300 volunteers have been withdrawn from the Middle East because of the war situation. Another 3,000 return to the United States every year after completing their assignments in about 70 countries."Our job in the '90s is to put knowledge gained in Haiti to work in tough high schools in Harlem; to put the skills acquired in Poland to use in Peoria . . . to carry the torch of voluntarism from Thailand to an elementary school in Topeka," Coverdell said.

The Peace Corps in 1986 created a small program, Fellows-USA, to help make up for the shortage of science and mathematics teachers in this country.

The program has expanded to 11 areas including Los Angeles, Miami, New Orleans, Atlanta and Washington, D.C. By 1992 the Peace Corps expects to have it going in nine more places, with "a couple of hundred" of its veterans teaching and studying at the same time, officials said.

Coverdell asked the mayors to help find universities and private contributors to spread the program.

He said Peace Corps veterans are especially qualified to teach Americans about the rest of the world. About one-third have had experience as teachers. They have served in more than 100 countries and speak about 200 languages and dialects.

"The Peace Corps must be involved in the battle to prepare America's schoolchildren for the many new opportunities and challenges in this rapidly changing world," Coverdell said.

"Why? Because one in seven Americans can't identify the United States on a world map."