TODAY

*A briefing on the status and future of the Strategic Defense Initiative, sponsored by the American Society of Mechanical Engineers, begins Tuesday at 8:15 a.m. at the Pentagon City Quality Inn, Arlington. Registration and a reception will be held today at 7:30 p.m. Phone 785-3756.

*Nutrition issues in developing countries are the topic of a public symposium sponsored by the Food and Nutrition Board at 9 a.m., National Academy of Sciences, 2100 C St. NW. Speakers include John Kenneth Galbraith of Harvard University, James Grant of UNICEF and Abraham Horwitz of the Pan American Health Organization. Phone 334-2138.

*Officials from NASA, the National Oceanic and Atmospheric Administration and Ford Aerospace hold a news conference to discuss the new generation of GOES weather satellites, 11 a.m. at the National Press Club.

*Former national security affairs adviser Robert C. McFarlane speaks before the World Affairs Council of Washington, 6 p.m. at the Mayflower Hotel. Phone 293-1051.

*The decorated White House Christmas tree is unveiled. TUESDAY

*The National Archives sponsors a lecture with retired U.S. Navy captain Roger S. Pineau and author John Costello on new discoveries about World War II naval intelligence, noon in Room 105 of the archives.

*The president meets with the congressional leadership, holds a Cabinet session on the budget and hosts a Christmas party for members of Congress and their families.

*Education Secretary William J. Bennett, Librarian of Congress Daniel Boorstin and James Duffy, ABC president for communications, hold a 10 a.m. news conference at the Library of Congress to discuss a national campaign addressing major social problems.

*Sen. Daniel J. Evans (R-Wash.) and Gov. Charles S. Robb (D-Va.) hold a news conference to discuss proposals by the Committee on Federalism and National Purpose for reordering relationships among federal, state and local governments, 10:30 a.m. at the National Press Club.

*The Agriculture Department reports on Dec. 1 crop production. WEDNESDAY

*James P. Grant, executive director of the United Nation's Children's Fund, holds a news conference to discuss the "State of the World's Children" report, at 10 a.m. in the Mike Mansfield Room of the Capitol. Phone 547-7946.

*The results of a study of the Great Lakes Water Quality Agreement will be discussed at a 10 a.m. news conference in Toronto, Canada. Phone Gail Porter at the National Research Council in Washington at 334-2138 for details.

*The Southeast Women's Employment Coalition sponsors a news conference to release data on the representation of women in federally funded road and highway construction projects, 10 a.m. at the Hotel Washington. Employment experts will also discuss the potential impact of changes in federal affirmative action guidelines. Phone Lisa Lederer or Susan Bales at 337-0855.

*The Department of Commerce reports on third-quarter merchandise trade, balance of payment basis.

*The President's Blue Ribbon Commission on Defense Management will hold open meetings Wednesday and Thursday from 8:30 a.m. to noon in the Main Auditorium of the Department of Interior. Phone 638-0799.

*Litigation insurance is the topic of a nationwide conference beginning at 9:30 a.m. at the Washington Convention Center. Phone 484-5623.

*The Bureau of the Census reports on October housing completions. THURSDAY

*The Administrative Conference of the United States, a federal agency that makes recommendations regarding the efficiency, adequacy and fairness of the precedures administrative agencies use in carrying out programs, holds a press briefing at 12:30 p.m. in Conference Room A of the Federal Home Loan Bank Board, 1700 G St. NW. Phone Sue Boley at 254-7020.

*Health care cost containment is the topic of a seminar sponsored by the Workplace Health Fund, 4 to 6 p.m. at the International Union of Operating Engineers Building, 1125 17th St. NW. Phone 842-7832.

*NASA scientists hold a news briefing on the agency's programs involving Halley's Comet investigations, 1 p.m. at 400 Maryland Ave. SW.

*The Federal Reserve Board reports on money stock measures and factors affecting reserves of depository institutions. FRIDAY

*The Institute of Internal Auditors sponsors a seminar entitled "Information Systems and the Auditor," 8:30 to 11:30 a.m. at the National Press Club. Phone Glen Langlois at 694-5813.

*The Bureau of Labor Statistics issues a release on November producer prices.

*The Cato Institute sponsors a policy forum entitled "In Pursuit of True Equality for Black Americans," noon to 1:30 p.m. at the institute, 224 Second St. SE. Phone 546-0200.

*The Bureau of the Census issues a release on October manufacturing and trade: inventories and sales.

*M. Peter McPherson, head of the Agency for International Development, holds a news briefing on the International Conference on Oral Rehydration Therapy, noon at the Hyatt Regency Capitol Hill.