The United States has started discussions with West Germany about possibly moving some U.S. equipment and troops out of Germany to help establish an American military presence in Southwest Asia, reliable sources said yesterday.

The sources added that West German Foreign Minister Hans-Dietrich Genscher, who yesterday completed a visit here, assured U.S. officials that the Bonn government will be "understanding and cooperative" if it becomes necessary to reduce U.S. military strength in Western Europe temporarily to counter Soviet moves in the Persian Gulf area.

In addition, the sources said, the discussions with Genscher have made it much more likely that the West German government, despite strong domestic opposition, will fall into line behind President Carter's efforts to block the Olympic Games from taking place in Moscow this summer.

Although Genscher made no commitments about the Olympics, the sources said he left Washington deeply impressed by the Carter administration's determination to prevent the Soviet Union from hosting the games.

As a result, the sources continued, there are strong grounds for believing that Genscher will use his influence within Chancellor Helmut Schmidt's government to argue that, if the United States refuses to participate in the Olympics, West Germany will have no choice but to go along.

According to the sources, Genscher was surprised and strongly impressed by seeing at first hand how strongly American public opinion supports Carter's stance on the Olympics.

Another factor that reportedly made a deep impact on Genscher was the amount of attention that has been focused in the United States on the way in which Hitler used the 1936 Olympic Games in Berlin to glorify the Nazi movement. Because of that historical background, the sources said, Genscher apparently concluded that any German government will find it difficult to argue that political considerations can be kept separate from the Olympics.

The Olympics have become the sumbolic centerpiece of an internal debate within West Germany about how far that country should go in support of the U.S. confrontation with the Soviet Union over the invasion of Afghanistan.

As the country whose territory forms the front line between East and West Europe, West Germany counts the United States as the ally on which its security ultimately depends.

But, as the country whose "eastern policy" of reconcillation with the communist block launched the detente era a decade ago, the West Germans also have a compelling interest in keeping open their lines to Moscow.

Schmidt and Genscher head a coalition government containing powerful elements that believe deeply in the slogan, "Detente is indivisible," and those elements fear this indivisibility would be shattered by actions like a West German boycott of the Olympics.

The result has been a situtation that has seen Bonn giving rhetorical support to U.S. calls for a strong western response to the Soviets but holding back from commitment to actions that go beyond symbolic gestures. It was largely in an effort to overcome some of these differences that Genscher came here for two days of talks with Carter, Secretary of State Cyrus R. Vance and other key administration officials.

In what the sources said was the most important aspect of these talks, the two sides began preliminary discussion of the possibility that the United States might have to draw down its stocks of weapons and other equipment in West Germany in order to fulfill its offers of military aid to Pakistan quickly and perhaps later to other Southwest Asia and Middle East countries.

The discussions also are understood to have included the possibility of U.S. troops being moved out of West Germany if future developments lead to establishment of U.S. bases in that area or if they are needed there for other emergencies.

Such moves would mean at least a temporary weakening of the forces the United States has committed to North Atlantic Treaty Organization defenses in Europe. However, the sources said, Genscher assured the administration that, if the need arises, Bonn would support the temporary shift of U.S. forces out of Europe.

According to the sources, Genscher also reaffirmed Bonn's commitment, as part of the division of labor being worked out within NATO to deal with the Persian Gulf to assume special responsibilities for economic assistance to Turkey in an effort to strengthen it against internal turmoil and Soviet pressure.

In a related development yesterday, a spokesman for Roy Jenkins, British president of the European Economic Community Commission, said the nine-nation West European group is moving quickly to strengthen ties with Turkey and Yugoslavia, another troubled country on the Soviet border.

Jenkins also was in Washington for talks with administration leaders, and his spokesman, Roger Bacon, said the situation in Southwest Asia has caused the European Economic Community to put special stress on bolstering Turkey and concluding a new trade link with Yugoslavia, which is independent of Moscow despite its communist form of government.

The administration also revealed yesterday that it is sending out a new group of high-level emissaries as part of its effort to rally support behind its effort to contain the expansion of Soviet influence in Southwest Asia.

The White House announced that former defense secretary Clark Clifford will go to India on Jan. 31 to discuss with Prime Minister Indira Ghandi India's concerns about an infusion of U.S. arms into neighboring Pakistan disturbing the balance of power on the Indian subcontinent.

State Department sources said Deputy Secretary of State Warren M. Christopher will visit Pakistan shortly for further talks on the $400 million military and economic assistance package being readied by the United States. The sources said Christopher will make the trip after an upcoming conference in Pakistan of Islamic nations to discuss the Afghanistan situation and its potential dangers to neighboring Moslem states.