National security affairs adviser Robert C. McFarlane and White House communications director Patrick J. Buchanan clashed sharply yesterday over one of the major speeches President Reagan is to give during his approaching European trip, according to well-informed administration sources.

The sources said McFarlane complained at yesterday's senior staff meeting that speech writers under Buchanan's direction had prepared an audience-rousing speech more suitable to a political campaign for Reagan to give when he speaks to the European Parliament in Strasbourg, France, on May 8. McFarlane instead had argued for a "presidential-type" policy speech that would take a longer view and be nonconfrontational in tone, like the one Reagan gave to the British Parliament in 1982.

A senior official said yesterday that McFarlane rewrote two earlier drafts over the weekend to eliminate some anticommunist rhetoric and produce a more "thoughtful and reflective speech" on U.S.-Soviet relations.

An administration official often critical of Buchanan said the original speech would have been more appropriate for delivery to "the American Legion in Philadelphia" than to the European Parliament.

Buchanan has followed a policy of not returning reporters' telephone calls.

In recent weeks McFarlane reportedly has become steadily more critical of Buchanan and the speech writers who report to the communications director for positioning Reagan in ways the security adviser considers unnecessarily combative and ideological. Officials said McFarlane and Richard R. Burt, assistant secretary of state for European affairs, have viewed the Strasbourg speech as an opportunity for Reagan to give a lofty address on postwar Europe, reaffirming the traditional goals of the U.S.-European alliance. Instead, they said the speech writers prepared a draft that, according to one official, was "heavy on anticommunism and applause lines" and lacking in more reflective themes. McFarlane complained and it was reworked, but a second draft did not make the changes he had sought. Officials said McFarlane worked on the speech and presented a third draft yesterday.

One official said McFarlane quietly presented the revised draft at the senior staff meeting, without criticizing Buchanan's previous version. But the official said Buchanan "goaded" McFarlane, saying, "I thought we worked all this out with Dick Burt." An official said McFarlane, usually soft-spoken, became "furious" when Buchanan persisted in defending earlier versions and finally snapped, "Speech writers aren't supposed to make policy."

White House deputy chief of staff Michael K. Deaver, who has been at odds with Buchanan, supported McFarlane, saying the purpose of the address is to set a tone for U.S.-European relations rather than win applause back home.

Sources said that the dispute was left to chief of staff Donald T. Regan to resolve and that the draft he is to give the president essentially incorporates McFarlane's changes. Reagan sometimes changes a speech once the final staff draft is presented to him.

Yesterday's conflict provided further evidence of a growing dispute within the Reagan administration between Buchanan, who has urged a hard line in public speeches, and a group of White House officials who believe that the president is poorly served by a confrontational style. The dispute has erupted particularly over speeches about Central America, where McFarlane privately has contended that the more combative tone has undermined efforts to reach a consensus that would provide "humanitarian aid" for the rebels fighting the leftist Nicaraguan government. But yesterday's clash shows that the dispute extends to issues beyond Central America.

Some officials believe it is likely to be the prelude to more fundamental clashes between Buchanan and McFarlane, and that such disagreements eventually may require a deeper involvement by Regan in the speech-preparation process. One senior official said the problem was one of tone as much as ideology. "The speech writers want a game-buster every time," he said.