The administration has decided to rush $10 million to $12 million in emergency airlift, food and supplies to the all-African peace-keeping force being created to replace Libyan troops in Chad, administration sources said yesterday.

The administration's plan of tangible support for the African effort, which is being discussed with members of Congress before a public announcement, became known as Vice President Bush and Secretary of State Alexander M. Haig Jr. met here with Sudanese President Jaafar Nimeri, one of those most deeply concerned.

Nimeri, in an interview with The Washington Post, praised the planned U.S. aid as "a very important effort." He said the speed of a U.S. response, even more than its scope or size, is important for the success of the Organization of African Unity's peace-keeping effort.

Nimeri reported Libyan-generated trouble on Sudan's western border with Ethiopia, whose foreign minister yesterday charged the United States with encouraging "aggression." Details on Page A26.

The Sudanese leader, whose eastern border area was bombed and his regime threatened in recent weeks by Libyan forces in neighboring Chad, also charged that the current Libyan pullback is "a tactical withdrawal, not a strategic withdrawal," with the aim of returning to the battleground later.

According to Nimeri, Libyan leader Muammar Qaddafi recently made his first payment of about $100 million to Ethiopia under the three-month-old alliance of Libya, Ethiopia and South Yemen.

He added that Libyan weapons are starting to arrive at Ethiopian ports for shipment to tribesmen along the Ethiopian-Sudanese border.

"I'm sure Qaddafi did not pay this money just for friendship," said Nimeri, long an outspoken foe of the Libyan leader. "We are asking Ethiopia if they know about these weapons. If they do know this, they are hiring out their country to be terrorists" in return for Libyan cash, he said.

Especially since the assassination six weeks ago of Egyptian president Anwar Sadat, Haig and other senior U.S. officials have expressed serious concern about the security of Sudan, which occupies an important piece of geography just south of Egypt on the Nile.

Haig, meeting Nimeri in Cairo during Sadat's funeral, publicly promised to accelerate U.S. economic and military support for Sudan and subsequently sent two U.S. Air Force radar surveillance planes to watch Sudan's borders with Libya and Chad.

Nimeri, who is here for a medical checkup and meetings with senior officials, praised the "very satisfactory" U.S. political response since Sadat's death. He said he believes it was a factor in Qaddafi's decision to pull back in Chad, thus decreasing the external danger to Sudan for time being.

Nimeri was grateful but less enthusiastic about the amount or speed of U.S. economic and military aid to his country, saying he has not received everything he is seeking.

Nimeri said he is asking this week for new Export-Import Bank loans and that U.S. oil firms be encouraged to explore and develop Sudanese energy resources. On the military aid front, he said "we did not receive anything up to now" despite the quick action promised by Haig.

Nimeri said strong U.S. statements and gestures were among four reasons why Qaddafi decided on the pullback in Chad. The others, he said, were OAU political pressure, the high cost including 2,100 unannounced military deaths in the Libyan expeditionary force and growing internal trouble inside Libya.

The proposed U.S. aid for the OAU force, which has been under discussion here for several weeks, is to include a U.S. airlift into Chad of troops of several African countries; tents, bedding and field kitchens for those forces, and food to support them. If members of Congress approve, the money will be taken from existing accounts in the federal budget, official sources said. France and other European countries are expected to contribute to the OAU effort.