President Reagan will confer with leaders of six industrialized democracies at the United Nations this month in an effort to demonstrate allied unity in advance of his November summit meeting with Soviet leader Mikhail Gorbachev, White House officials said yesterday.

A senior administration official said the meeting also will help blunt "the traditional Soviet public-relations effort to drive a wedge between the United States and Europe. It's important to maintain East-West solidarity on the main East-West issues involving strategic stability."

White House deputy press secretary Edward Djerejian announced the meeting, saying that "the president wanted to have a dialogue with the leaders of the western summit nations" in advance of his meeting with Gorbachev and that their presence at the United Nations in October provided "a timely opportunity for a working session."

The nations are Britain, Canada, France, Italy, West Germany and Japan, whose leaders meet every year with the U.S. president at economic summits. Frequently, the side discussions at these economic summit meetings focus on U.S.-Soviet relations.

An administration official said Reagan wanted to reassure the leaders of these nations that the United States remains pledged to their defense despite his commitment to the Strategic Defense Initiative (SDI), also known as "Star Wars," which he views as a potential "defensive shield" for the United States.

U.S. officials repeatedly have told concerned Europeans that Reagan's commitment to the SDI does not mean any lessening of traditional U.S. commitments to Europe.

Yesterday the president emphasized his commitment to the European alliance and tried to take the edge off Gorbachev's visit to France this week in an interview with and written response to the French newspaper Le Figaro.

"It is particularly important that Mr. Gorbachev realize that our alliance stands strong and that the Soviet Union has to do its part -- as we are ready to do ours -- in a serious, honest effort to build more constructive relations," Reagan said in one of the responses. " . . . I know from my many meetings with President [Francois] Mitterrand that he is a very forceful advocate of his views, that he favors a strong united and secure West and that he has no illustions about the Soviet system."

France, along with Canada, has declined to have any governmental connection with the SDI. Britain and West Germany, with Italy expected to follow suit, have been supportive of strategic defense research but have not endorsed testing or deployment. Japan has favored research in general terms.

At a meeting Friday with Soviet Foreign Minister Eduard Shevardnadze, the president reaffirmed his commitment to the SDI, and administration officials contend that the Soviets are vigorously pursuing a strategic defense plan of their own.

Reagan has invited the six leaders to meet with him on Oct. 24, when he also is scheduled to address a special commemorative session of the U.N. General Assembly. They are among 70 heads of state or government expected to attend a special session commemorating the 40th anniversary of the United Nations.

The White House had expected to make the announcement of the meeting of the seven leaders later in the week as one step in the "public diplomacy" campaign leading up to the Nov. 19-20 summit in Geneva between Reagan and Gorbachev.

But the administration's plans changed abruptly yesterday when a spokesman for the West German government in Bonn announced the meeting and said that West German Chancellor Helmut Kohl would attend. This sent officials in Washington scrambling to make their own announcement.