Ronald Reagan has decided to name former South Carolina governor James Edwards as energy secretary and former Nixon antipoverty chief Philip V. Sanchez as secretary of housing and urban development, transition sources said yesterday.

The president-elect also indirectly confirmed his intention to name staunch conservative James G. Watt as interior secretary, praising him for "fighting environmentalist extremists."

Meanwhile, Reagan's selection of an agriculture secretary has been delayed by a power struggle that pits Sen. Bob Dole (R-Kan.) against former agriculture secretary Earl Butz, each pushing his own candidate for the job, transition sources said. Dole's candidate, John R. Block, the Illinois state director of agriculture, was once the front-runner, but his chances have been dimmed by a heavy Butz campaign of propaganda and persuasion in favor of his former deputy secretary of agriculture, Richard Lyng. Lyng also served as California's director of agriculture under Reagan from 1967 to 1969.

Reagan transition officials also disclosed procedures by which the incoming White House staff will attempt to exert unprecedented control over the appointment of sub-Cabinet officials for each department.

According to several top transition officials, each Cabinet nominee will be given lists of from three to eight names recommended for appointment for each sub-Cabinet post. If the Cabinet secretaries prefer someone who is not on the list, they will be required to go back to White House officials -- presumably counselor Edwin Meese III and James A. Baker III -- for approval.

The selection of Edwards as energy secretary will please southerners, especially Sen. Strom Thurmond -R-S.C.), who had complained to Reagan officials that there was no southerner in the first batch of Reagan Cabinet appointments. The selection of Sanchez, a Mexican American, will likewise please Hispanics.

But the selection of these men also means that as yet the Reagan Cabinet has no black or women members, with the only remaining vacancies being at education -- the department that Reagan has vowed to abolish -- and at agriculture, plus the Cabinet-level post of United Nations ambassador.

In choosing Sanchez for HUD, Reagan passed over Jewel Lafontant, a Chicago lawyer who is both black and a woman, and who had been considered a strong candidate for the job.

Yesterday, in a breakfast meeting with reporters, chief of staff Baker promised flatly that there would be a black in the Reagan Cabinet. Republican sources said yesterday that Thomas Sowell, a conservative black economist and a senior fellow at the Hoover Institution at Stanford University, was considered the most likely choice for the education job, although the decision was not final.

Elizabeth Dole, former member of the Federal Trade Commission and the wife of the Republican senator from Kansas, and Barbara Thompson, Wisconsin superintendent of public education, had been under strong consideration for the education post. But Republican sources said that Elizabeth Dole has most recently been under consideration for the United Nations ambassadorship, and has been considered as well for a top White House staff job.

The president-elect, speaking with reporters in Los Angeles, wound up indirectly confirming his unannounced but already controversial selection of James G. Watt of Denver as interior secretary. Watt was pushed hard for the job by Joseph Coors, the very conservative Colorado brewer and a member of Reagan's informal "kitchen cabinet" of advisers. Watt is the head of a legal foundation that has devoted itself to suing the Interior Department and fighting government efforts to give utility rate breaks and other benefits to the handicapped, the elderly, and the poor.

Yesterday, Reagan was asked by a reporter whether he thought someone who had been fighting environmentalists should be named interior secretary. Reagan was quick to amend the question. "Fighting environmental extremists," he said.

And while not mentioning Watt by name, Reagan clearly was talking only of Watt as he went on to say, "I think he's an environmentalist himself, as I think I am.I think my record proves it -- and his will also."

Reagan's appointment of Edwards as his secretary of energy may prove somewhat awkward. The South Carolinian, an oral surgeon by profession, is an expert on drilling teeth, not oil wells. Yesterday, Reagan defended Edwards' qualifications to head the Energy Department. "This has been a very vital interest of his," Reagan said. "As governor he was involved in the governors' organization on energy problems."

Reagan made his comments in support of Edwards and Watt after emerging from a meat locker where he had carried two bags full of beef and veal raised on his Santa Barbara ranch.

In 1977, Edwards came under considerable criticism from black leaders after a series of statements he made during a trip to South Africa. The black leaders claimed his statements were "racist." Edwards claimed his statements were "misunderstood."

On that trip, Edwards had said that "the black influence in American politics prevented the white South African government from getting its fair share of sympathy and understanding," that some American inner cities are "very much worse" than the black township of Soweto in Johannesburg, where riots had recently occurred in protests of South Africa's apartheid policies, and that he was "shocked and pleasantly surprised to see how much money is being spent on health services, education, and housing for blacks" in South Africa.

Sanchez, 50, was director of the Office of Economic Opportunity under President Nixon. At one point during his tenure, he clashed with the then-governor of California, Ronald Reagan, who resented the way the federal antipoverty agency was trying to exert control over programs in California. Sanchez went on to serve as U.S. ambassador to Honduras and later Colombia, as the Nixon administration went on to dismantle the OEO.

Reagan transition officials sought to emphasize yesterday that Cabinet officials will still have a voice in the picking of their sub-Cabinet subordinates, even though they will be working initially from a list of names supplied by the Reagan forces. "A Cabinet secretary can still make a case for someone he wants," said one official.

In the autumn issue of The Washington Quarterly, retired general Alexander M. Haig Jr. -- now Reagan's nominee to be secretary of state -- addressed himself philosophically to this sub-Cabinet selection issue, a problem that he, as it turns out, must face.Said Haig:

"A Cabinet officer -- especially a strong one -- will insist on having a considerable voice in the selection of his immediate subordinates. However, a president [or his immediate staff] will need to ensure that all those chosen for sub-Cabinet positions are essentially in accord with the president's basic goals and philosophies -- and so not unduly reflect the personal hobby horse of any individual Cabinet member or other senior administration official."

And, analyzing the bureacratic struggle in terms of military strategy, Haig added: ". . . A president who neglects his troops, especially those who have followed and supported him in adversity, will soon face adversity alone."