The White House said yesterday that the 13-day trip of First Lady Rosalynn Carter to Latin America, which starts Monday, will include "substantive" discussions as well as goodwill diplomacy.

President Carter, in announcing May 3 that his wife would visit seven countries, referred to her as "a political partner of mine" and said she would "conduct substantive talks with the leaders of those countries."

But some Latin Americans privately expressed displeasure that Carter would send a woman, particularly one who is not an expert on inter-American affairs, to discuss serious policy issues. Later, White House press secretary Jody Powell referred to the trip as a goodwill gesture, which seemed to downgrade its importance.

Yesterday, however, a senior National Security Council official said at a White House briefing that Mrs. Carter "intends to spread goodwill and discuss serious issues."

Robert Pastor, senior NSC staff member of the inter-American affairs, said "most Latin American heads of state view women in a stereotypical mold."

He said Mrs. Carter would make the trip for the President "not as an ambassador, but as his representative, as his wife." Pastor, conceding that Mrs. Carter "is not a negotiator," said, however, she could guarantee that head of state would be given a fair hearing" and that their views would be transmitted to the President.

On her 12,000-mile swing, the First Lady will visit Jamaica, Costa Rica, Ecuador, Peru, Brazil, Colombia and Venezuela.

Pastor outlined these purposes of the trip:

"To convey to Latin American governments a sense of what this administration is all about . . . its priorities and goals and how (it) will face issues affecting Latin America.

"To talk about the new directions the President has sketched in his Pan American Day speech." In that address on April 14 Carter told the Organization of American States he would seek Senate ratification of an inter-American treaty on human rights and of an agreement that would prohibit U.S. deployment of nuclear weapons in Latin America. He also promised to consult Latin leaders on major policy issues.

"To hear the comments and reactions of Latin American leaders on where the United States is going right and where it's going wrong."

Pastor said Mrs. Carter would discuss such issues as economic problems, relations with Cuba, the Panama Canal and foreign assistance. Earlier, one expect who briefed her said she probably would not discuss U.S. opposition to Brazil's controversial plan to buy a nuclear processing plant from West Germany, the issue that has severely strained U.S.-Brazil relations.