President-elect Bush, with his Cabinet still less than half filled, says John Tower would be an outstanding secretary of defense and he doubts that an FBI check has turned up anything to disqualify the former Texas senator.

Bush said Wednesday, however, that he has not yet decided who will run the Pentagon, although sources said Tower remained the leading candidate.With eight more appointments to go, Bush hopes to complete naming his Cabinet before Christmas.

Bush tapped Clayton Yeutter on Wednesday as the sixth member of his Cabinet. Yeutter, the U.S. trade representative for President Reagan, will be secretary of agriculture.

After three years in government, Yeutter had wanted to return to private business. Standing alongside Bush at a news conference, Yeutter said there were "only a few people in the world who could convince me to carry forward in another stint in government, but you're one of those few."

Bush also said he would name a black to his Cabinet. He has been urged by some black supporters to name Louis W. Sullivan, a black who is president of Morehouse School of Medicine, as secretary of Health and Human Services.

In addition, The Washington Post reported in Thursday's editions that another black, Julius W. Becton Jr., a retired three-star Army general who heads the Federal Emergency Management Agency, is the top contender to head the Veterans Administration, and that a Hispanic member of the Federal Communications Commission, Patricia Diaz Dennis, is a candidate to head the Labor Department.

Also, an aide to Sen. Lowell P. Weicker Jr., who lost his re-election bid last month, confirmed that the senator has met with Bush about possibly taking over the National Oceanic and Atmospheric Administration.

Covering a wide range of topics at the news conference, Bush also:

-Hinted his administration will seek a delay in February's resumption of arms control talks with the Soviet Union. "There is no way that we are going to have by Feb. 15 or 16 a detailed point-by-point program on arms talks," Bush said.

-Said Palestine Liberation Organization leader Yasser Arafat had made "some movement" in a speech Tuesday but "not enough" to warrant direct dealings with the PLO by the United States. Later, however, President Reagan said the United States would enter into "a substantive dialogue" with the PLO.

-Said Vice President-elect Dan Quayle's role would be "very much like the Reagan-Bush relationship." He said Quayle would be a "key player" in national security affairs if he wants to be and that there may be specific assignments in other areas.

-Said he would not seek substantial cuts in existing farm programs but didn't say what he meant by substantial. "I do not believe we will balance the budget eventually on the backs of farmers," he said.

Yeutter, 58, a onetime Nebraska farmer, was the fifth veteran of the Reagan administration to join Bush's incoming Cabinet.

Asked how Yeutter's selection squared with his promise to bring a new team of people to Washington, Bush said, "Well, his face is familiar, but the job is very different than being trade representative."