Negotiations between South Africa and Angola on a formula for Namibia's independence are showing slow but clear signs of progress, and the United States is trying to assist the process, a senior U.S. official said yesterday.

The official, who asked not to be identified, briefed reporters on the findings of Chester A. Crocker, assistant secretary of state for African affairs, who visited South Africa last week.

"There is no dramatic announcement," the official said. "But we certainly believe there is enough potential to continue trying to move the process."

The talks on independence for Namibia, a predominantly black territory controlled by South Africa since World War I, began moving again last November after more than two years of deadlock.

The delays had centered on South African demands, backed by the United States, that 25,000 Cuban troops be removed from neighboring Angola before Namibia -- once called South West Africa -- can become independent.

Angola has signaled that it agrees to the principle of Cuban withdrawal as "part of the package" to bring peace to the region, and its stance has been endorsed by Cuban President Fidel Castro.

However, the U.S. official conceded, considerable work has to be done to find a blueprint and a schedule for achieving these goals.

The official also acknowledged that the United States yesterday closed the liaison office it had set up in the Namibian capital of Windhoek to monitor the withdrawal of South African troops from southern Angola under the agreement made by South Africa and Angola in Lusaka a year ago.

The Lusaka accord calls for South Africa to pull out the forces sent into Angola to counter guerrillas of the South West Africa People's Organization (SWAPO), a Namibian nationalist force that Pretoria regards as Marxist.

In return, Angola is supposed to curb SWAPO incursions into Namibia from Angolan territory.

The withdrawal was to be monitored by a joint Angolan-South African commission and was supposed to be completed last April. But the South African troops remain in Angola.

Despite that, the senior U.S. official disputed contentions that the Lusaka agreement has failed and that the closing of the American liaison office in Windhoek is an admission of that failure.

Instead, he said, if the South African withdrawal does take place soon as the United States hopes, the United States will be able to monitor its progress with personnel from the U.S. Embassy in Pretoria.

"There is no advantage for South Africa to have the process nearly complete but not all the way completed," the official said.

"No party wants a situation where there's no basis for continued stability," he said.

"For twelve months, there has been no fighting. In moving South African forces from Angola to the border, they want to sustain that peace and not go back to the status quo ante of cross-border raids and counter raids."

The official said it would help the negotiations on Namibia and Cuban withdrawal if the South African disengagement was completed.

But, he added, "the two matters are not linked. The Lusaka agreement is not tied to a Namibia agreement."