WASHINGTON (AP) _ New spending restrictions are in effect at the Pentagon until at least June 30 to make sure the military stays within the bounds of a deficit-reduction compromise crafted by Congress and the president in December.

The restrictions, ordered Friday by Deputy Defense Secretary William H. Taft IV, put a halt to purchases of office supplies, banned overtime and limited civilian hiring for at least the next six weeks.

All new contracts for research and development work also have been put on hold temporarily, as have purchases of everything from magazine and newspaper subscriptions to television sets, library materials, recreation equipment, lawn mowers and furniture.

Tools, paint, lumber, air conditioners and forklifts also are on the prohibited list for the time being, as are plans to lease cars, office space or computer equipment. --- Law Makes It Easier For WWII Veterans To Receive Disability Benefits

WASHINGTON (AP) - A new law will make it easier for an estimated 300,000 veterans of World War II to receive disability benefits for exposure to radiation from the atomic blasts in Japan or from nuclear test explosions.

Legislation signed Friday by President Reagan bypasses in some cases the usual requirement that veterans claiming disability benefits must prove the disability was connected with their military service.

The new law applies primarily to cancer of various organs. The Office of Management and Budget said more than 300,000 veterans would be affected by the legislation, and the first-year cost was estimated at $65.6 million.

Norman Solomon, Washington spokesman for the Alliance of Atomic Veterans, called the new law ''a long overdue step toward taking care of a very large and serious problem.'' --- Better Explanation Required On Adjustable Rate Mortgages

WASHINGTON (AP) - Savings institutions have until Oct. 1 to begin complying with new rules that require them to offer better explanations of their adjustable-rate mortgage programs.

The Federal Home Loan Bank Board, which regulates 3,120 federally insured savings institutions, said S&Ls must provide the information either when a mortgage application form is offered or before the borrower pays any non- refundable fees, whichever occurs first.

Lenders must include a historic example of how mortgage payments would have changed over the past 15 years using the index or formula on which interest rate changes are based. S&Ls must also notify borrowers at least 25 days in advance of any change in monthly payments.

The new rules were adopted last week and became effective Monday, however the bank board did not announce adoption of the regulation until Friday. --- VA Mortgage Interest Rate to Rise

WASHINGTON (AP) - The Veterans Administration is raising its maximum interest rate for federally backed VA home mortgages to reflect recent increases in interest rates in financial markets.

The agency said Friday the rates would rise by one-half percentage point to 10.5 percent, effective Monday.

The Federal Home Loan Mortgage Corp. said Friday that the national average for 30-year, conventional mortgages - those without government guarantees - rose to 10.52 percent this week from 10.40 percent last week.

The VA said that effective Monday a variety of other mortgage rates will also rise by one-half percentage point. Graduated payment mortgages will increase to 10.75 percent, home improvement loans will rise to 12 percent and loans for mobile homes will increase to 13 percent.

The VA rates apply to new loans, not existing ones. VA mortgages peaked at 17.5 percent in September 1981 before beginning a decline and reaching a low for this decade of 8.5 percent in January 1987.