WEST BERLIN, JUNE 10 -- White House advancemen, seeking to make the biggest possible splash for President Reagan's speech at the Berlin Wall Friday, persuaded skeptical West Berlin officials to invite a larger crowd than the Germans wanted and to stage the event opposite the visually impressive but politically sensitive Brandenburg Gate, U.S. and West Berlin officials said today.

Some West Berlin authorities were concerned that the East Germans and Soviets would consider it unduly "provocative" for Reagan to speak with the gate, a classical-style arch in East Berlin, directly behind him, city officials said. The 196-year-old gate, in the center of Berlin, stands only yards beyond the Wall dividing the city. As the best-known site along the Wall, it is a particularly emotional symbol of the city's division.

The West Berliners proposed the nearby Reichstag building, that formerly housed the German parliament, as the site for Reagan's speech. But the White House insisted from the start on the location opposite the Brandenburg Gate because it had "the highest recognition factor," a U.S. official said.

The Americans also succeeded in having invitations to hear the speech sent to 40,000 persons, whereas the West Berliners favored a crowd of 20,000 to make it easier to guarantee security. "All of these 40,000 have to go through a police check. That was a problem from our point of view," a city official said.

The differences, which were not a source of major friction between Washington and West Berlin, were resolved amicably last month, the U.S. and West Berlin officials said. It was clear from the officials' remarks that the crowd size was a greater problem for the West Germans than the site of Reagan's speech.

Reagan will stand 50 yards from the Wall with the gate as his backdrop on Friday afternoon when he delivers what U.S. officials here described as a significant foreign policy address.

"He will make some important, Berlin-related initiatives and also focus on East-West relations," a U.S. official said. He declined to discuss what the president planned to say.

Reagan will stop here for between four and five hours on his trip back to Washington from the Venice economic summit.

He visited West Berlin in 1982 and thus will become the first president to come here twice while in office. Most presidents since 1945 have traveled to West Berlin to reaffirm the West's commitment to preserve this enclave 110 miles inside East Germany.

The West Berlin government has brought in 1,000 policemen from West Germany as reinforcements to help contain expected violence by young, anti-Reagan protesters. Long lines have formed at highway entry points in recent days as police have taken extra pains to check identity documents and search cars.

Anti-U.S. demonstrations led to violent confrontations when Reagan was here last time. Police have granted permission for several protests, but the authorities are bracing for street clashes.

Demonstrations have been banned in an area of several blocks around the site of Reagan's speech. The largest legally authorized protest, organized by 130 groups led by the pacifist-ecologist Alternative List party, is scheduled for Thursday evening.

Reagan follows Queen Elizabeth II and French President Francois Mitterrand in making a visit this year during Berlin's 750th anniversary. The three heads of state lead the allied powers that have had ultimate responsibilty for governing West Berlin since the defeat of Hitler's Germany.

Reagan will follow a new allied policy, adopted this year, of paying an informal visit on West German President Richard von Weizsaecker in von Weizsaecker's official Berlin residence.

The gesture is aimed at underlining allied support for West Berlin's special ties with West Germany. Moscow, which has responsibility for East Berlin, contends that West Berlin is a unique entity independent of West Germany.