The chairman of Sudan's transitional military council today announced resumption of diplomatic relations with Libya and the dispatch of an envoy to Ethiopia in an apparent effort to enlist their help in ending the debilitating two-year-old rebellion in southern Sudan.

According to reports from Cairo, Khartoum-based Libyan exiles of the National Salvation Front also have left Sudan at government insistence. Under president Jaafar Nimeri, who was overthrown 18 days ago in a coup led by Gen. Abdel Rahman Sawar-Dhahab, the front regularly was allowed to broadcast propaganda hostile to Libyan leader Muammar Qaddafi from here.

Efforts to end the revolt by Christian and animist forces in southern Sudan against the predominantly Moslem north so far have proven illusive. The rebels reportedly have had the support of Libya and Ethiopia, while Ethiopian rebels and Sudanese exiles reportedly had the backing of the Nimeri government.

In another possible shift, the military council also is reported to have shelved U.S. plans for increasing food shipments through Sudan into rebel-held areas of Ethiopia to feed famine victims there.

Informed sources said U.S. officials had presented the plans to the military council recently but had not pressed for adoption. Nimeri's government had favored expanding so-ca oontinuing contacts" were in progress with the American-educated Garang in Ethiopia, the general added, "I have not personally met him or heard any specific thing from him."

Despite Garang's repeated demands that the military council resign in favor of civilian rule now as his price for negotiating an end of the rebellion, Sawar-Dhahab said, "There are indications that he will come to an understanding and sit down with us at the negotiating table."

The general provided no details to substantiate that claim.

Many Sudanese have said that potentially the Ethiopian authorities could be more helpful than Libya in dealing with Garang since he uses their territory as a sanctuary.

Sawar-Dhahab said the southern military situation was "reassuring" and "completely calm" despite Garang's claims of renewed hostilities after a week-long unilateral cease-fire following Nimeri's overthrow on April 6.

This afternoon, for example, Garang's radio station broadcasting from Ethiopia claimed his forces inflicted "heavy casualties" on government troops in a battle in Upper Nile Province yesterday.

The radio announced that Garang has initiated contacts in the field with junior officers, noncommissioned officers and enlisted men of the Sudanese Army. The effort, presumably to subvert the troops, was said to have "reasonably good prospects" of success.

The radio repeated recent threats to carry the war to the north for the first time.

Sawar-Dhahab repeated his "desire to improve" previously bad relations with the Soviet Union and said relations "of friendship" with the United States were "solid." He thanked "our American brothers for their continuing support" in dealing with the drought and the economic crisis.

The general appeared to be softening critical remarks two days ago by civilian Prime Minister Gizzuli Daffa-Allah, who asked for a revision of "close ties" with the United States as part of an overall foreign policy reappraisal aimed at making Sudan genuinely nonaligned after Nimeri's increasingly pro-American policies.