The Sudanese government yesterday ordered a partial rollback in food price increases in an effort to stem a general strike that has paralyzed the capital of Khartoum, and concern mounted within the Reagan administration over the fate of President Jaafar Nimeri's embattled pro-American regime.

Khartoum's airport remained closed, and telecommunication links to the outside world were cut for a third day. But diplomatic reports reaching here said the government announced lower prices Thursday night for three basic commodities -- bread, soap and edible oils -- in a bid to quell the disturbances that began 11 days ago in the capital and have developed into a general strike.

The violence was sparked by steep price increases, particularly for bread and gasoline, that Nimeri imposed in a bid to free $181 million in American economic aid frozen because of political and economic uncertainties in Sudan.

After expressing confidence for the past week in Nimeri's ability to weather the latest challenge to his 16-year-old regime, U.S. officials yesterday began making more guarded assessments, saying they thought much will depend on how Nimeri handles the situation once he returns to Khartoum.

Nimeri left Washington yesterday and was expected to stop in Egypt en route home.

Khartoum was reported generally quiet but still in a "state of total paralysis" yesterday, the Moslem holy day, with police and security forces patrolling the streets. The British Broadcasting Corp. said there was a growing fuel shortage in the capital, apparently a result of the general strike, which has affected all public services and many government offices. Only one section in the city, where a hospital is located, had lights, according to reports reaching the State Department.

Nimeri, who was here on a private visit for medical treatment, met for 45 minutes yesterday with Secretary of State George P. Shultz before heading home. He was expected to stop in Cairo to consult with Egyptian President Hosni Mubarak, his closest Arab ally.

A Sudanese Embassy statement said the results of Nimeri's annual medical checkup indicated that he is "in very good health." It also pronounced his 10-day visit here "successful," noting that he had kept to his prearranged schedule, a comment apparently meant to indicate that he was not unduly concerned about the situation at home.

A Secret Service spokesman, meanwhile, confirmed that Nimeri had received "some threats" while here but refused to comment further.

U.S. officials yesterday said they were "concerned" about what appeared to be sustained, and even spreading, demonstrations in Khartoum and the increasing political nature of the protests. One official, who asked not to be identified, described the situation as "worrisome but by no means irreversible" and said the Reagan administration had no plans to reverse Monday's decision to release $181 million in U.S. economic aid, which had been delayed until Nimeri instituted some economic changes.

The official noted that the Sudanese army, which is crucial to Nimeri's fate, appeared to be remaining loyal and that the police and other security forces involved in handling the street disorders were acting professionally and with restraint. There were no signs of the army or police switching sides, he said.

"The real issue now is what will be the reaction to his return," another official said, suggesting that it would either bring the political crisis to a climax or cow the opposition.

Price increases of up to 60 percent on items such as bread and gasoline, which sparked the riots, were part of a larger reform ending state subsidies on gas and almost all food. The measure was sufficient to convince the U.S. government to release $67 million in 1984 economic support funds and to begin planning for the disbursement of $114 million earmarked for Sudan this fiscal year.

The ultimate effect of the price cuts on the attitude of the United States, and more important, the International Monetary Fund, toward Nimeri's request for leniency and more donor aid to assist his drought-afflicted country through its economic crisis remains to be seen.

Sudan is $120 million in arrears on its payments to the IMF, which has led western nations to freeze hundreds of millions of dollars in assistance, although emergency food aid for more than a million Sudanese and other drought victims continues.

U.S. officials said it was "too early to tell" how the administration and other western donors, let alone the IMF, would react to the price rollback because it was not known whether other steps had been taken to cut government spending to compensate for reintroduction of subsidies on some food items.

"It depends on whether other adjustments are made in the budget to reduce the deficit," one official said.