After an internal debate, the Reagan administration has approved the shipment of Claymore mines to Salvadoran military forces but has refused to supply white phosphorous grenades.

The request for the munitions last fall by the U.S. Embassy in San Salvador touched off one of the latest of many debates among U.S. officials about the tactics, weaponry and political impact of Salvadoran military.

U.S. Ambassador Deane Hinton and the Salvadoran forces are reported to be dissatisfied with Washington's refusal to supply the incendiary grenades. Hinton reportedly made a case that the grenades were needed to help specially trained forces break off contact with guerrillas and to signal friendly forces.

The Pentagon and the State Department's Bureau of Politico-Military Affairs backed the request but several other State Department bureaus, including the Latin American regional bureau and the Human Rights bureau, argued successfully that use of the fiery grenades as anti-personnel weapons would have devastating effect on civilians. Moreover, the State Department bureaus argued that a strong public reaction to the supply of the weapons could undermine U.S. efforts in El Salvador.

A central worry among policy makers is that the Salvadoran military situation is essentially stalemated and that, over time, the government side will be worn down, leading to the eventual victory of the 5,000 to 6,000 guerrillas.

There is agreement in the Pentagon and State Department that no significant advances are being made against the insurgents, despite large-scale U.S. aid, training and technical advice for the 33,000-man Salvadoran army and security forces.

"The Salvadoran government forces are not operating at anywhere near their potential," a State Department official said. "But the guerrillas are operating pretty close to their potential."

In a report on the military situation Feb. 2, the Pentagon's chief Central American expert, Deputy Assistant Secretary of Defense Nestor D. Sanchez, said the Salvadoran armed forces have been "in a reactive mode," partly because the attention of the military high command has been diverted from the military field to domestic political matters.

"At the very time the high command should have been adjusting its tactics to the guerrilla threat, it has found itself increasingly drawn into the political infighting that is characteristic of an embryonic democracy," Sanchez told the Senate Foreign Relations Committee.

There is a consensus in government that little or no major change can be expected before the current uncertainty is resolved about the future of Gen. Jose Guillermo Garcia, the defense minister and strongest military figure. Many reports suggest that Garcia is likely to step down due to internal maneuvering within the next few weeks.

Ebbing support for the Salvadoran efforts in Congress, as well as the perception of stalemate, has given rise to discussions in the administration of new initiatives in the diplomatic field.

Secretary of State George P. Shultz and other officials have contested a report that Assistant Secretary of State Thomas O. Enders has recommended a "two-track" policy including a bid for negotiations with the political arm of the Salvadoran insurgency. The United States for many months has favored political reconciliation in El Salvador essentially on the government's terms, while opposing a negotiation between government and rebels to work out shares of power.

State Department officials said that one proposal under recent discussion is for renewed efforts in the international arena to induce Nicaragua to stop support of Salvadoran guerrillas, restrict its military relations with Cuba and the Soviet bloc and move toward political reconciliation at home, in return for improved relations with the United States, including U.S. economic aid.

Such an arrangement was first offered by Enders in August, 1981, and again through Mexico last March. Nicaragua responded last year by asking for broad diplomatic talks with the United States covering all outstanding issues. Washington has ignored this call for a high-level meeting.

In order to provide more weapons and equipment to the war effort, the Reagan administration is preparing to ask Congress for about $80 million in military aid for El Salvador in fiscal year 1984, a sum considered certain to run into strong Capitol Hill opposition.

Last year the administration asked for $60 million but failure to pass a foreign aid bill resulted in a continuing resolution that provided $25 million for El Salvador.

The Claymore mines and white phosphorous grenades were among the weapons requested by San Salvador last fall as part of a major augmentation of military supplies. At the time both items were withheld due to political sensitivity in Washington. The U.S. Embassy in Salvador appealed this decision, arguing that the weapons would be used for operations by well-trained Salvadoran forces in guerrilla-controlled areas that are not heavily populated.

Claymore mines, which were used extensively in the Vietnam war, are generally used for ambushes and protection of static positions. Some Claymore mines had been supplied to Salvadoran forces for perimeter defense after the guerrilla attack on Ilopango air base near San Salvador in January, 1982. But there was concern in Washington that the supply of 300 more mines would lead to increased civilian casualties and a tendency of the Salvadoran forces to occupy heavily fortified, static positions.

On the other hand, some officials argued that such standard weaponry as the mines should not be withheld from Salvadoran forces. "It would be ridiculous to deny them Claymore mines. The guerrillas have plenty of them," said an official.

White phosphorous rockets and canisters had been supplied to Salvadoran forces earlier for marking targets for artillery and air strikes, but white phosphorous grenades are considered less effective for this purpose while at the same time subject to misuse as an anti-personnel weapon.

During international negotiations on the rules of warfare in the 1970s attempts were made to outlaw white phosphorous munitions because of their incendiary nature. The United States opposed such a prohibition, arguing that its weapons were not used as anti-personnel devices but for marking positions and targets.