An internal rift developed within the South African government today over the country's policy on the use of nuclear energy.

Finance Minister Owen Horwood, who has his influential power base as leader of the ruling National Party in Natal Province, said that if South Africa wants to develop a nuclear bomb capacity it "will jolly well do so" despite international criticism.

A few hours later, however, South African Foreign Minister R.F. (Pik) Botha saod in an interview with The Washington Post that his government stands by Prime Minister John Vorster's declaration last week that South African "nuclear energy [will] be used solely for peaceful purposes."

Botha himself, however, was critical of the role the United States played in the nuclear controversy and said: "America cannot pressure us. We will not allow it."

Horwood's speech clearly reflected the growing resentment here against the United States and other Western powers that were recently reported to have acted in concert with the Soviet Union to stop South Africa from setting off its first atomic explosion.

Speaking at a National Party Congress, Horwood said, "I think it is time we told [President] Carter and a few other people that, if we did at any time wish to do other things with our nuclear potential, we will jolly well do so according to our own decisions and our own judgment."

He went on, "If he [President Carter] thinks he is free to dictate to us, then he is simply saying that 'Might is right' and that he can prescribe moral norms and lay down the law to everyone else. I reject that position absolutely and entirely. We are a sovereign, autonomous country."

Foreign Minister Botha also took strong exception to a recent Washington Post story detailing how the United States, France, West Germany and the Soviet Union had acted together to pressure South Africa into halting its preparation for an atomic bomb test.

"Our reponse was base on a decision mad by us," Botha said. "Furthermore, it was based on facts as they existed and still exist."

The refusal of the U.S. government to deny The Post report, he added, had stirred the anti-American lobby insided this country and that "detrimentally affects our relations in various fields, particularly if these reports are not repudiated by spokesmen of the U.S. government.

Pressure, Botha said, "is not the way bilateral discussions take place. That has never been the way the American government has acted toward other government."

He also took issue with The Washington Post over a story on Monday's talks held here between Vorster, British Foreign Secretary David Owen and U.S. Ambassador Andrew Young, saying that it left the impression that Vorster had "ignored" Young.

He said the conversation between Vorster and Young had been cordial and courteous and that there was no question of a South African slight of the U.S. ambassador, who was meeting the prime minister for the first time.

He confirmed, however, that most of the talking had been between Vorster and Owen since the latter was making the presentation of the latest Anglo-America plan for a constitutional settlement of the Rhodesia dispute. Young has deliberately kept a low profile in the current joint peace initiative to underline the American attitude that it is and should be a British-led one.

It appeared from Botha's remarks, however, that the South African government is as eager as Young seems to be to overcome the diplomatic incident earlier summer over the terms of a visa allowing the ambassador to visit here.

Yesterday, Young met for an hour with Interior Minister Connie Mulder, who is responsible for immigration matters, among other things. Although neither side said what the meeting was about, it was widely believed to have stemmed from the incident.

Today, the Anglo-American delegation led by Owen and Young left for Dar es Salaam and further talks with Tanzanian President Julius Nyerere. Nyerere and four other "front-line" leaders met with Owen and Young in Lusaka, Zambia, last weekend.

The stop in Dar es Salaam on the way to Nairobi was unscheduled, and seemed to indicate a possible new development in the complicated negotiations still under way over the Anglo-American proposals.

Observers here were left with the impression that the British and American proposals had run into sharp oppsition from Prime Minister Vorster. This, it was speculated here, may have led to reconsideration of the initial Anglo-American position that the proposals are essentially unchangeable and required discussions with President Nyerere.

Botha said after yesterday's talks that Owen and Young had not asked for a specific yes-or-no reply to the proposals, that South Africa had not given one, and that further consultations would follow.

The British and American envoys are scheduled to arrive Thursday in Salisbury to present the peace plan to Rhodesian Prime Minister Ian Smith before finally making it public.

The expectation here is that Smith will reject provisions calling for virtually dismantling the white-dominated Rhodesian army to make way for a black-controlled one to maintain order after the advent of black-majority rule.

The breakaway British colony, which unilaterally declared is independence in 1965, presently fighting for its life against nationalist guerrillas. There are roughly 270,000 whites and more than 6 millions blacks in Rhodesia.