MONTEVIDEO, Uruguay (AP) _ President-elect Julio Sanguinetti, whose inauguration next month will end nearly 12 years of military rule, said Monday he has chosen a supporter of his chief political rival to be foreign minister.

Sanguinetti, the victor in elections on Nov. 25, leads the centrist Colorado Party. In announcing his choice of 10 Cabinet members, Sanguinetti said his selection for foreign minister is Enrique Iglesias, an economist who traditionally supported the leader of the center-left National Party, Wilson Ferreira Aldunate.

Aldunate, Sanguinetti's chief political rival, was barred from running in the elections. The military regime jailed him on June 16 after he returned from 11 years in self-exile. He was released shortly after the balloting.

Sanguinetti had initially planned to form a ''unity Cabinet'' that would include members of other parties. However, the Nationals and the Broad Front, a coalition of leftist parties which make up the country's third most popular political group, refused to be included.

Iglesias agreed to his appointment with the understanding he was not formally representing the National Party on the Cabinet. Aldunate reportedly advised him to take the post.

Iglesias is executive secretary of the U.N.-Sponsored Economic Commission for Latin America, based in Chile.

Among the other Cabinet appointments were: for interior minister, Carlos Manini Rios; for defense, Juan Chiarino, former presidential candidate of the conservative Civic Union; for economy minister, Ricardo Zerbino; and to serve as both minister of justice and minister of eudcation and culture a jurist, Adela Reta.