Description The United States told Libya today that there could be ''serious consequences'' if it interfered with the Awacs surveillance planes that have been sent to help deter Libyan air attacks on the Sudan, an Administration official said.
The State Department and the Defense Department confirmed that two Awacs planes, along with tanker planes, had been sent to Egypt to join Egyptian fighters in patrolling Sudanese airspace.
Last Friday, a TU-22 bomber, said by the United States to belong to the Libyan Air Force, dropped five bombs on Omdurman, the Sudan's second largest city, and then returned to a base in the Kufra oasis of Libya.
The target of the attack apparently was the Omdurman radio station, but the bombs missed, and hit other buildings, killing five people.
Libya Denies Responsibility
Libya has denied responsibility for the attack. But Alan D. Romberg, a State Department spokesman, said today that ''we have good reason'' to believe Libya carried out the raid.
''Following the unprovoked attack on the Sudan by a Libyan aircraft on March 16, the Egyptian and Sudanese Governments have requested our assistance to bolster the capability of Egyptian and Sudanese air defense systems by providing early warning of air attacks,'' Mr. Romberg said.
''Awacs will be part of combined air defense operations being carried out by Egypt and the Sudan. The purpose of these operations is to deter sustained attacks by demonstrating that the three countries can rapidly put in place the assets necessary to deal with such aggression.''
Mr. Romberg said the note to Libya, in the absence of diplomatic relations, had been conveyed through Belgium, which represents American interests.
Another official said the message was, ''Our planes are there and don't mess with them.''
''We told the Libyans that we are deploying our own military aircraft in the region and any action against them could have serious consequences,'' the official said.
The Awacs have two missions: to serve as long-range reconnaissance planes and as command centers directing interceptor fighters against enemy targets. Because the Sudan has virtually no air defenses of its own, Egypt, which has a defense treaty with the Sudan, is responsible for flying interceptor planes in Sudanese airspace and for providing ground air defense, State Department officials said.
If the Awacs were to come under attack from Libyan planes, it could lead to the involvement of American planes aboard carriers in the Mediterranean. In February 1983, when Awacs were sent to Egypt because the United States feared a Libyan attack on the Sudan, the carrier Nimitz was moved closer to Libyan waters. Long-Term Aid Being Studied
Mr. Romberg said the United States was also ''examining what longer-term assistance we could provide the Sudan in the air defense area.''
Another official said the Sudan needed radar and antiaircraft weapons, either missiles or guns. The Sudanese are to receive a squadron of American F-5's, but only two have been delivered so far.
''They had some Soviet radar, but it is inoperative,'' one official said, ''because they have no spare parts.''
The Sudanese have been pressing the United States for weeks to speed up weapon deliveries to help them defend themselves against Libyan and Ethiopian help to insurgents in the southern Sudan. The Libyan bombing attack, Mr. Romberg said, has somewhat changed the situation because it made it important suddenly to send the Awacs to meet an immediate problem. Concern Over Surprise Attack
''There is no evidence of preparation for a massive attack,'' he said, ''but, as the attack of last Friday shows, there can be surprise attack and we are concerned about that sort of thing.''
American officials stressed, as they did last weekend, that the aid was aimed solely at external sources of trouble and was not meant to support the Government in Sudan's civil strife.
The United States and other powers, the officials said, have urged the Sudanese Government to be conciliatory toward Christians and pagans in the south who have risen in arms the imposition of Moslem law was ordered throughout the country last fall. The rebellion also followed the division of the Sudan's Southern Region into three provinces, in contradiction to an accord that ended a civil war in 1972.
The Libyan leader, Muammar al- Qaddafi, has long been accused of plotting against President Ghafar el-Nimeiry of the Sudan, and Colonel Qaddafi has made no secret of his hostility. Speech by Qaddafi Quoted
On March 2, Colonel Qaddafi said in a speech:
''We tell the agents in the Sudan that we are allied with the popular revolution in the southern Sudan for the sake of liberating Sudan inch by inch, just as Lebanon was liberated.
''The United States cannot save that mean man who is hiding in Khartoum. This is because, with the revolutionary forces in Ethiopia, in the Arab homeland, the revolution in Libya has decided to ally itself with the revolution in the southern Sudan. The peoples will march forward and will develop a people's war of liberation in Sudan, and tomorrow in Egypt and in every area that America seeks to dominate.
''We must force America to fight on a hundred fronts all over the earth. We must force it to fight in Lebanon, to fight in Chad, to fight in the Sudan and to fight in El Salvador.''
Libya has been charged with sending arms to all those places, in support of insurgencies.