The United States has decided to send Zaire about $13 million more in "nonlethal" military aid but has rejected that country's request for arms and ammunition, the Senate Department announced yesterday.

The U.S. action is intended to show support for the government of President Mobutu Sese Skeo, officials said, without involving the United States directly in his battle with Katangan rebels based in neighboring Angola.

State Department spokesman Hoddling Carter III said Zaire's request for weapons was rejected becuase "we see a need for an end to fighting, no an expansion of the fighting."

he new aid shipment will contain a $9 million C-130 military cargo plae which has long been on order, plus radio equipment, spare parts and related equipments. Finaning will come from the $30 billion. U.S. military aid program from Zaire which was previously approved by Congree. The new shipment adds to two panelloads of spare parts, radio and other greater that were previously sent as a cost of about $2 million.

In an interview with Arnaud de Borchgrave of Newsweek. Mobutu recently said he is "bitterly" disappointed" by U.S. failure to give him stronger support in the face of Katangan "invaders." Mobutu claimed the fighting is part of a Soviet-Cuban "grand design" in Africa. "I just wish that the U.S. were not so afraid to stand up and be counted," he said.

Mobutu said he had received a message from Secretary of State Cyrus R. Vance saying "there was no question of abandoning me" but he complained about the implementation of the U.S. statement.

At the White House, deputy press secretary Rex Granum said "we do not see the (Zaire) situation as an East-West confrontation," Granum said the shipment of nonlethal supplies is intended to help stabilize the situation in Zaire so that diplomatic mediation efforts by Nigeria can go forward.

The State Department spokesman said the U.S. assistance announced yesterday was not coordinated with Morocco, which has sent troops to aid Zaire, or with France, which is airlifting military equipment.

The spokesman also said no U.S. technicians will be sent to operate the equipment in Zaire, and that there are no U.S. military advisers there.

Sen. Dick Clark (D-Iowa) and some other members of Congress have cautioned against U.S. military involvment in the Zaire conflict. Clark said some aspects of a civil war are involved, because the rebel forces are native Katangans who fled across the border to Angola some years ago.

President Carter, during his political campaing last year, opposed the Ford administration's proposed arms sales to Zaire and Kenya as "fueling the East-West arms race in Africa even while supplanting our own allies - Britain and France - in their relations with these African states."