The chief of the South African defense force, Gen. Constand Viljoen, said on his return from a visit to his troops in Namibia last night that he did not expect them to be withdrawn from the disputed territory in 1983.

Although he stressed it was for the government, not the military, to decide on the timing of a settlement, Viljoen said South Africa should not "rush into a settlement within the next year" but rather should take its time to reach a long-term solution.

This was the clearest indication yet that South Africa does not fully share Washington's continuing optimism that a settlement in Namibia, also known as South-West Africa, is attainable in the near future.

Officially the Department of Foreign Affairs identifies itself with Washington's bullish attitude, but key government and military officials have made statements revealing an inner skepticism.

This has caused continuing speculation here that South Africa does not want a settlement in Namibia right now and has pressed along with the United States for a prior withdrawal of Cuban troops from neighboring Angola because the South Africans believe this effectively will stall the negotiations.

Observers point out that South Africa wants a delay partly to consolidate reforms being made to its own constitution and partly because the political parties it favors in Namibia are in disarray and would probably be beaten in elections by the South-West Africa People's Organization (SWAPO), which Pretoria regards as Marxist.

At the end of October, Defense Minister Magnus Malan, who was Viljoen's predecessor as chief of the general staff, expressed doubts about getting Angola to agree to a Cuban withdrawal. He said he did not believe the Soviet Union would allow it.

Malan also indicated that a SWAPO victory in Namibia would be unacceptable to South Africa. He was speaking on the eve of Vice President Bush's tour of Africa to try to win suppport for the U.S. stand on the Cubans, and Foreign Minister Roelof F. (Pik) Botha hastily issued a statement that South Africa still favored elections.

Botha met with Secretary of State George P. Shultz soon afterward and echoed U.S. optimism that agreement on the Cuban issue was possible.

But Viljoen's statement indicates that he does not anticipate a settlement within the next year. As a key member of the National Security Council, Viljoen is extremely influential and he is close to Prime Minister Pieter W. Botha.

Asked after landing at Pretoria's Waterkloof Air Force Base whether he thought this was the last Christmas he would spend with his troops in Namibia, Viljoen replied: "No, I don't think so.

"I would hate us to rush into a solution within the next year, only to find ourselves going back in after two years when South-West Africa is again burning."

Pointing to Angola, Mozambique and Zimbabwe as examples that independence did not necessarily bring peace, Viljoen said it would be better for South Africa to work for a long-lasting solution in Namibia.

"We in South Africa must grasp the importance of reaching a long-lasting solution, so that the people of South-West Africa can live in peace for a number of decades at least after we withdraw.

"We are capable of maintaining the military situation for a long time, or until such a lasting solution is arrived at," Viljoen said.