The Reagan administration has notified Congress that it intends to supply $9.1 million in equipment and weapons to El Salvador's police in the months ahead, despite protests that the police continue to abuse human rights.

A State Department letter to Congress Aug. 31 said Secretary of State George P. Shultz would authorize the funds within 30 days "for the purpose of training and equipping {Salvadoran} public-security forces."

Congressional sources said that several members of the House will ask the Appropriations Committee to delay the proposal until there is a closer examination of the State Department's contention that the Salvadoran police have improved their rights record sufficiently to be entrusted with U.S.-supplied weapons. Some senators may also oppose the funds.

Supplies will include Remington police shotguns, 9 mm Beretta pistols, M16 rifles fitted with sniper scopes, vehicles, clothing and communications equipment, according to the State Department.

The letter was intended to fulfill a congressional requirement that the department certify El Salvador "has made significant progress during the preceding six months in eliminating any human-rights violations, including torture, incommunicado detention, detention of persons solely for nonviolent expression of their political views or prolonged detention without trial."

"The assistance program {for the Salvadoran police} has met, or exceeded, expectations across the board and has uniformly fulfilled the criteria of human-rights improvements on the part of the public security forces," an accompanying report from the department said.

That assessment was disputed yesterday by Americas Watch, a private organization that monitors human rights in Latin America. In a detailed report issued Aug. 29, Americas Watch said there is evidence to support charges that Salvadoran security forces, including the Treasury Police, have committed murder and other rights abuses.

For several years, Congress barred the use of U.S. military aid for police. After the June 19, 1985, murder by leftist insurgents of six Americans, including four Marine guards at the U.S. Embassy in San Salvador, Congress permitted use of some military assistance funds in the 1986 and 1987 fiscal years for police activities, with the proviso that the State Department certify every six months that human-rights progress is being made.