President Hosni Mubarak of Egypt began a three-day official visit to Washington yesterday with meetings with administration officials in preparation for his meeting today with President Reagan.

The Egyptian leader is in Washington seeking to elicit a new American activism in the Middle East peace process, and $1.9 billion in additional economic and military aid for his hard-pressed nation.

The administration is anxious to hear from Mubarak the details of his recent proposal for talks leading to direct Arab-Israeli negotiations and starting with "discussions" between a joint Jordanian-Palestinian delegation and the United States.

U.S. officials want to know what he has in mind by proposing such preliminary discussions, which Palestinians would be included in this delegation and whether this is a new Egyptian gambit to get the United States talking to the Palestine Liberation Organization.

"We have no interest in meeting with a PLO team if there is not an explicit acceptance of U.N. Security Council resolutions 242, 338 and articulation of Israel's right to exist. That hasn't changed," a senior administration official said.

Yesterday, Mubarak met with Defense Secretary Caspar W. Weinberger, Secretary of State George P. Schultz, Treasury Secretary James A. Baker III, Commerce Secretary Malcolm Baldrige, U.S. Trade Representative William E. Brock and Agency for International Development Deputy Administrator Jay F. Morris, among others.

Mubarak also saw International Monetary Fund Managing Director Jacques de Larosiere, World Bank President A.W. Clausen, a delegation of American Jewish leaders and a delegation from the Congressional Black Caucus.