Britain and the United States are being widely accused of deliberately playing down the results of last weekend's talks with Rhodesian guerrilla leaders in order to pave the way for eventual Western support of the Rhodesian internal settlement.

Zambian, Tanzanian and black nationalist leaders say they cannot understand why the Rhodesian Patriotic Front is being blamed for escalating its demands at the meeting in Dar es Salaam, when in fact, they say, the Rhodesian guerrilla leaders made several major concessions.

"Why aren't British and Americans telling the world that the conference was a success," a top Tanzanian official asked in an interview in Dar es Salaam.

The answer, in the view of many African leaders, is that while Secretary of State Cyrus Vance may be eager to reach an accommodation with the Patriotic Front that would make the guerrillas a party to a Rhodesian settlement, British Foreign Secretary David Owen is of a different mind.

"The Patriotic Front is not a problem," the Tanzanian official said. "The British are. There are people in Britain who want the option of accepting the internal settlement. They would be happy if the Anglo-American proposals would melt away."

George Silundika, publicity secretary for Joshu Nkomo's wing of the Patriotic Front, charged that the British wanted last weekend's meeting to fail, and "even sabotaged the final joint communique."

Zambian and nationalist sources here feel it is unfair that the Patriotic Front is being blamed for excessive militancy when it has been the only party to show any willingness so far to negotiate with the British and Americans on the basis of the Anglo American proposals.

Furthermore, they point out, the Front has made numerous concessions to accomodate the two Western powers, and committed itself last weekend to attend a conference of all the Rhodesian parties.

On the other hand, the black and white leaders inside Rhodesia have rejected outright the Anglo-American proposals, signed their own agreement for a transfer to black majority rule in defiance of London and Washington, and have refused so far to attend an enlarged conference.

Nor, in the Rhodesian nationalist view, have Britain and the United States lived up to their own commitment under the Anglo-American proposals to take "appropriate steps" to remove white Prime Minister Ian Smith from power in Salisbury.

"President [Kenneth] Kaunda [of Zambia] was right last fall when he kept asking the British how they planned to remove Smith." remarked Silundika. "They haven't done it, and they will not do it."

Vance and Owen were reported to have felt let down by Tanzanian President Julius Nyerere and the other leaders of front-line African states because the Rhodesian guerrilla leaders last weekend did not accept the Angola-American proposals in toto. Vance and Owen talked of "escalated demands" and "fundamental changes" in the nationalist negotiating position.

But the front-line and nationalist view of what happened at the Dar es Salaam conference is quite the opposite. It holds that the nationalists, in fact, made several important concessions while Owen in particular was of a complete agreement.

"The British were completely insen-fact, made several important concessions while Onen in particular was determined to forest all the reaching of a complete agreement.

"The British were completely insensitive and unappreciative of whatever concessions we made," said Silundika, who attended the meeting. "Each time we made a concession, they stepped backward and wanted more concessions."

By contrast the Front negotiators found Vance far more appreciative of their concessions.

"Vance gave the impression he was prepared to reflect on the concessions we made," said Silundika."He was more interested in moving toward some kind of mutual accomodation."

The British-American view is that the Patriotic Front continues to balk at several key provisions in the Anglo-American proposals regarding the powers of the proposed British resident commissioner who would rule Rhodesia during the transition to majority rule the makeup of the military and police force during that period.

The nationalists, however, feel they have made major concessions by agreeing to a U. N. peacekeeping force, and agreeing that the British resident commissioner would have ultimate responsibility for law and order, defense and foreign affairs during the transition.

At the Malta conference last January, the nationalists had rejected both these points, and demanded that they themselves "superinted" the entire transitional period.

The upshot of all the haggling between the two Western powers and the Patriotic Front is that Zambian newspapers are asking whether the British and Americans are sincere about their own proposals.

The Zambian Daily Mail's editor, Vincent Mijoni, in a rare commentary, wrote Thursday that the agreement March 3 between Prime Minister Smith and three black leaders had caused "jubilation" in the West because it offered the hope of keeping "communist-backed Patriotic Front from taking power in Rhodesia.

The whole British-American objective now, he concluded, was to play for time until the Salibury agreement takes root and gains international acceptance.

"The game of the West," he said, is "to play with the Rhodesian thing for as long as possible" until opposition to the internal settlement fizzles out.

But he warned that this was a dangerous game. Both the Patriotic Front and the front-line states were certain to become increasingly dependent on Soviet arms and Cuban aid if the fighting continued.

"When the worst will come to the worst," he concluded, "it will be very dificult for the world to escape an East-West confrontation over Rhodesia."

Washington Post Special Correspondent Martha Honey in Dar es Salaam contributed to this story .