Vice President-elect Walter F. Mondale will visit Japan and Western Europe this month in a prelude to a possible economic summit conference that could be held as early as May, President-elect Jimmy Carter announced tday.

Carter said the week-long trip to Japan, West Germany, France, Great Britain and the headquarters of the North Atlantic Treaty Organization and the European Economic Community in Brussels will take place during the first week he and Mondale are in office. They will be sworn in on Jan. 20.

Speaking to reporters outside his home, Carter said no decision has been made to hold an economic summit conference of the leaders of the major non-Communist industrial nations. But he sounded as if he expects such a gathering to take place this year and said that he would attend it.

Carter said that Mondale will discuss with the foreign leaders "better means by which we might coordinate our NATO policies, deal with the problems of the increased oil prices and also share with them some of our potential plans at that point for helping resolve the problems surrounding Cyprus with Turkey and Greece, the Mideast and the southern African question."

He said other trips are being planned for early in his administration by Secretary of State-designate Cyrus R. Vance and others. Carter said he will attempt to keep his travel abroad to a mininum during his first year in office, preferring instead to invite foreign leaders to visit the United States.

One exception, he added, would be a trip to the proposed economic summit conference.

Carter said that he expects to meet with Soviet leader Leonid I. Brezhnev before next fall and that he hopes there is "substantial progress" in reaching a new Strategic Arms Limitation Talks (SALT) agreement before then.

Discussing messages between him and Soviet officials since his election, Carter said there has been "no major breakthrough on SALT yet" and that "we have not gotten down to any detailed discussion with the Soviet Union, of course, at this point."

He said the messages recently delivered to Vance and Secretary of State Henry A. Kissinger by Soviet Ambassador Anatoliy Dobrynin "have been encouraging, but I think that's to be expected.

"When you get down to the detailed implementation of the general commitments, that's when the problems come in," Carter added.

Mondale's trip is the latest example of Carter's often-stated determination to give his Vice President a major and highly visible role in the administration.

Carter said that preliminary arrangements for the trip have been made and that next week he will telephone British Prime Minister James Callaghan, West German Chancellor Helmut Schmidt, French President Valery Giscard d'Estaing and Japanese Prime Minister Takeo Fukuda to discuss the Mondale visits.

Carter noted that "all four of those gentlemen speak fluent English" and said the telephone calls will be his first direct contact with any of them since the Nov. 2 election.

Mondale's trip, according to Carter is designed to provide the leaders of the United States' major allies with details of "what I and the United States Congress proposes to do about the stimulation of our economy" and to discuss with them "the hopes of our own administration in international matters, particularly relating to economics and the alleviation of tension in rare trouble spots."

Neither a time nor a place for an economic summit conference has been set, but Carter said it could be in the "latter part of May or sometime in June." Japan has been most often mentioned as the likely site. President Ford attended similar economic summit conferences in France, and most recently, in Puerto Rico.

On another foreign policy subject, Carter said he does not want to "preempt the British government in (its) leading role" in seeking a solution to tensions in Rhodesia and elsewhere in southern Africa. He said he wants to inform the British that "we do back their efforts" and to "offer our good services" in seeking a solution.

Carter also said that he:

Expects to announce next week the names of his top White House aides and the person he has chosen to be trustee of his financial holdings while he is in office. The trustee is expected to be Carter's longtime friend and adviser, Atlanta lawyer Charles Kirbo.

Will meet early in his administration with the leaders of Canada and Mexico, a traditional gesture of friendship by a new President toward the United States' neighbors.

Still intends to issue a pardon to Vietnam war draft evaders during his first week in office but said that the extent and terms of the pardon have not been worked out.

After the monrning press conference, Carter spend much of today working on his inaugural address with Patrick Anderson, his principal speech-writer during the campaign. He has no scheduled appointments Sunday except his regular attendance at Sunday school and church services at the Plains Baptist Church.