The Reagan administration struck an extremely cautious note yesterday in its assessment of the military junta that toppled Sudanese President Jaafar Nimeri from power Saturday.

The State Department said it was too early to judge either the political orientation or intentions of the new regime despite its declared desire to maintain good relations with Washington and return the country to civilian rule.

State Department and Pentagon analysts appeared to be relieved by what they described as "moderate" and "conciliatory" statements coming from Gen. Abdel Rahman Sawar-Dhahab, the head of the four-man junta, over the weekend, but said many questions remained regarding the junta's policies and whether the military intended to remain in power.

State Department spokesman Bernard Kalb, noting that the new leadership faced a heavy agenda of unresolved economic and political issues, said it was too early for the United States to offer any detailed assessment of whether the new military government there was friendly.

He said, however, that the United States was ready to continue its more than $250 million-a-year aid program to the Sudan, including almost a million tons of regular and emergency food assistance. But another U.S. official said $114 million in economic support funds earmarked for this fiscal year can not be disbursed until a meeting of western donor countries is held to discuss an overall plan for economic recovery and debt rescheduling.

U.S. analysts seemed to agree that the four officers making up the new junta were basically "apolitical" and acted from a "sense of nationalism." They said they thought the four had acted less to install themselves in power than to "preempt any future violence," as one Pentagon source put it, when faced with the general strike that had paralyzed the Sudanese capital of Khartoum.

"I don't get the impression they are keen on ruling," said a State Department official.

Sawar-Dhahab, 51, the army commander-in-chief, reportedly was partly trained as a young officer at Fort Benning, Ga., and has visited here at least once since then, according to a Pentagon analyst. He and the other three members of the junta were all believed to be graduates of the Nasser Military Academy in Cairo.

The three others making up the junta were identified by State Department officials yesterday as Gen. Tajeldin Abdullah-Fadel, deputy army commander-in-chief; Lt. Gen. Mohammed Tawfik Khalil-Ibrahim, chief of logistics, and Lt. Gen. Josef Hussein Ahmed, director of armed forces administration. Together with Sawar-Dhahab, they held the top positions in the armed forces before the coup.

A Pentagon analyst said he believed Sawar-Dhahab, who was handpicked by Nimeri to take over a post he had previously held, was basically a very quiet person who tended to think through issues thoroughly before acting.

Describing the general as "a plodder," the analyst said he doubted Sawar-Dhahab had acted on his own and suggested other unknown officers were deeply involved in planning the coup.

The biggest question hanging over the new military group is whether it will in fact go ahead and hold elections for a return to civilian rule as it has promised.

The junta has dissolved the National Assembly; Nimeri's ruling party, the Sudan Socialist Union, and the cabinet, and has scrapped the constitution, leaving the country without major institutions.