In an effort to undercut Libya's growing influence in neighboring Sudan, Egypt has begun sending new arms shipments to Khartoum and has undertaken a diplomatic initiative aimed at reducing Ethiopian support for southern Sudanese rebels.

According to Egyptian Foreign Ministry sources and reports published in the semiofficial Cairo press today, a first planeload of Egyptian ammunition, guns and uniforms for the Sudanese Army landed in Khartoum yesterday.

A shipment of about 20 Egyptian-made armored cars will follow shortly, according to the official Middle East News Agency, as part of a military grant amounting to $10 million.

At the same time, Egyptian Foreign Minister Esmat Abdel-Meguid was in Addis Ababa yesterday, speaking with Ethiopian leader Mengistu Haile Mariam in an effort to persuade Ethiopia to curtail its extensive support for the Sudanese rebel forces of Col. John Garang, Foreign Ministry sources said. The official press here did not specify the nature of the 90-minute meeting in the Ethiopian capital.

The initiatives come as traditionally close Egyptian-Sudanese relations have shown public signs of strain and the competition for influence in the Sudan between Egypt and Libyan leader Muammar Qaddafi is heating up.

Egypt regards a friendly Sudan, on the upper reaches of the Nile, as vital to its interests. Cairo has always maintained a close watch on -- and often strongly influential role in -- Khartoum's affairs. But Qaddafi, who bitterly opposed Sudanese ex-president Jaafar Nimeri, saw the dictator's overthrow a year ago as a way to expand his own influence in Africa's largest country, the most strategically important in the region.

The situation is further complicated by Sudan's current elections, now about to enter the second week of voting. The winners are expected to replace the Transitional Military Council that has ruled the country since Nimeri's ouster.

Nimeri had extremely close relations with Cairo during his 16 years in power and now lives in exile here in Egypt. The members of the Transitional Military Council were generals closely associated with the dictator before moving at the last minute to oust him in the face of widespread protests and rioting.

The council's leader, Gen. Abdel Rahman Swar-Dahab, was considered particularly close to Cairo.

Many of the most prominent candidates for the new government, however, were exiled under Nimeri, and several were sheltered and supported at some point in their careers by Qaddafi. As one left-wing Egyptian political analyst put it, "In the Sudan, all opposition forces owed something to Libya, and Egypt was not very helpful."

Less than a week ago, Sudan's government shut down several offices established under a 1982 "integration" agreement between Egypt and Nimeri's government.

Meanwhile Sudan has sought and received extensive military aid from Qaddafi, who cut off his earlier support for Garang's rebels when Nimeri was deposed.

In late March, Sudanese Umma Party Leader Sadiq Mahdi, believed by many analysts to have the best chance of becoming Sudan's next prime minister, visited Qaddafi in Libya. According to Sudanese sources there, he was asking the Libyan leader to intercede with Ethiopia's revolutionary government in an effort to rein in Garang.

The Sudanese maintain that they are only pursuing a balanced foreign policy with their neighbors, and Mahdi is expected to visit here in the next few days, according to Egyptian Foreign Ministry sources.

But the timing of Egypt's new military shipments and Maguid's unexpected visit to Ethiopia suggest that Cairo has decided to take a more activist role in seeking closer ties with the incoming government despite past differences.

Press reports here revealed that Cairo supplied $14 million worth of arms to the military council in Khartoum last year.

In both cases, Egypt insisted that the equipment was not for use against the rebels, as the 1976 mutual defense pact under which it is furnished does not apply to internal unrest.