Rhodesian guerrilla leader Joshua Nkoma said yesterday that as far as he is concerned, the British-American plan for an all-parties conference to end the Rhodesian war is "dead now and buried" and that he would meet Rhodesian Prime Minister Ian Smith only at a "surrender" conference.

Nkomo's rejection of an all-parties conference is a further blow to the proposal, which has never had wide support and, in any case, was given little chance of success by most observers.

A British-American statement issued from London yesterday said the two countries would continue to work toward organizing an all-parties meeting as the only way to end the conflict, but privately U.S. officials are saying they have abandoned the effort.

Nkomo made it clear he was speaking only for himself in rejecting the all-parties conference, which both he and the guerrilla leader Robert Mugabe agreed last April, to attend, although they later attached restrictive conditions. The Americans and British had vainly tried to persuade Smith and his three black colleagues in the Salisbury government to attend the conference.

Although the all-parties conference has been the stated policy of the five so-called "frontline" African states most closely involved in the Rhodesian conflict - Angola, Botswana, Zambia, Tanzania and Mozambique - there no longer appears to be any unified backing for such a conference.

Nkomo was reacting yesterday to Smith's announcement Sunday that his government was imposing a form of martial law in parts of Rhodesia and that it had decided to "liquidate the internal working" of Nkomo's nationalist party, the Zimbabwe African Peoples' Union.

"Liquidation, what does that means?" Nkomo asked at a press conference. "It means war. I don't think there is anything to talk about . . . The British and Americans must accept this. The so-called all-parties conference is dead now and buried."

Nkomo's statement follows a recently aborted secret diplomatic initiative that brought Smith and Nkomo together at a meeting here last month in search of some agreement that might end the war. That effort was discontinued when it was disclosed by one of Smith's black colleagues in the multiracial government, the Rev. Ndabaningi Sithole.

Although Smith left open the door to a renewal of those talks in his speech Sunday and Nkomo yesterday did not rule them out, it appears unlikely that they will be resumed any time soon because of the increasingly hard line both men must take to satisfy their constituencies.

Independent observers believe that the time for secret talks has passed because of the growing trend to fight to the bitter end that is beginning to prevail in both the guerrilla forces and the Rhodesian government. Rhodesia is defended by a white-officered army that is 80 percent black.

Nkomo yesterday acused Smith of backtracking from what the guerrilla leader claims was a willingness at their meeting last month to hand over power to the Patriotic Front, the guerrilla grouping made up of Nkomo, with about 10,000 Soviet-armed guerrillas based in Zambia, and Mugabe, whose forces operate out of Mozambique.

"When I talked with Smith it was to discuss if he was ready to give up power. He said he was.Now within hardly two weeks, he is on the warpath and being on the warpath means there is no chance for a conference," Nkomo said.

"But if he says, 'We are surrendering, finished, that's the end of it,' then of course, we will accept the surrender," Nkomo said.

Nkomo said he would continue his war effort and predicted that the Salisbury government would be militarily defeated by April.

Nkomo, aiming at the already badly sagging white morale in Rhodesia, issued what he called "a word of advice" to travelers to "keep away from Air Rhodesia . . . because we will not know when they are carrying military personnel and equipment and when they are carrying (civilian) passengers."

The implication was that his forces will continue to regard civilian planes as targets for their ground-to-air missiles.

Nkomo, who said last week that his forces shot down a Rhodesian airliner carrying 56 persons, repeated his denial of Rhodesian claims and reports by survivors that his forces shot and killed 10 of the 18 people who had survived the plane crash.