President Carter tried to use a nationally televised news conference yesterday to advance his campaign against Ronald Reagan but was thrown on the defensive by questions about his earlier suggestion that Reagan was attempting to inject "racism" and "hatred" into the presidential contest.

Carter said he does not consider Reagan to be a racist, and he described his own campaign against the Republican nominee as "very moderate in its tone."

But the president was clearly annoyed by questions centering on his remarks Tuesday in Atlanta where he said Reagan had referred to the Ku Klux Klan and "states' rights" while campaigning and added: "Hatred has no place in this country. Racism has no place in this country."

Carter defended that, noting that he was speaking to a largely black audience of civil rights leaders who understand the meaning of such "code words." But when a questioner reminded him that Health and Human Services Secretary Patricia Harris first raised the issue of the klan and tried to link it to Reagan, the president appeared both annoyed and momentarily flustered.

"The press seems to be obsessed with this issue," he said.

Meanwhile, former president Ford threw himself into the controversy by accusing Carter of making "one of the lowest, most intemperate assaults ever made by a United States president" in his Atlanta comments.

"Mr. Carter does not just owe Gov. Reagan and the Republican Party an apology," Ford said in a statement issued by Reagan's campaign committee. "His intemperate and totally misleading statements demean the office of the presidency itself. And for that, Mr. Carter owes the American people an apology."

The news conference was the president's first in six weeks, and it was clear from the outset that Carter intended to use the session as a campaign vehicle. f

He opened with a lengthy statement on a series of positive national developments, including "some encouraging economic signs" that he detailed.

Carter said he was "standing firm against any tax reduction in this pre-election political climate," a reference to Reagan's support for a substantial tax-cutting to spur the economy.

Similarly, when asked about nuclear weapons policy, Carter who has portrayed Reagan as a potentially dangerous chief executive who might embroil the country in war, immediately linked the question to the presidential campaign.

"When anyone decides to run for president of our country with any expectation of being elected, the question of the use of atomic weapons has to be addressed . . . ," he said.

After the news conference, Reagan's campaign director, William Casey, said the president's opening five-minute statement was a "political commercial." Casey said he was asking the television networks for equal time for Reagan to respond.

The president maintained that he has not changed his assessment of the prospects for a resolution of the hostage crisis with Iran. He said the formation of a new parliament in Iran means "the situation has improved," but added that "I do not predict an early resolution of the issue because it's not in my hands unilaterally."

On other topics, Carter:

Predicted that the inflation rate will remain below the double-digit level the rest of this year and that the unemployment rate will not vary much from its 7.6 percent last month. He said some economic advisers have told him recently that the recession might be over, but he added, "I don't know."

Defended his support for loan guarantees to Chrysler Corp. as a "sound investment by the American government" to prevent "the loss of hundreds of thousands of American jobs among automobile workers and to keep a highly competitive automobile industry in our country."

"Reiterated his willingness to debate Reagan at the White House or "any other forum anywhere in this nation and as frequently as possible." But no change was indicated in his refusal to debate first with Reagan and independent candidate John B. Anderson, who will meet in their own head-to-head debate Sunday in Baltimore.

Much of the news conference was taken up with questions about the election. Carter denied one suggestion that he becomes "mean" while campaigning, asserting that an incumbent is subjected to "the most enthusiastic attacks" by his opponent but that when an incumbent responds "that's immediately given the highest possible notice as an attack on one's challenger."

"So I try to keep a moderate tone," he said. "I try to discuss the issues and I do not indulge in attacking personally the integrity of my opponents and I hope that I never shall."

In response to another question, however, the president fell back on his campaign rhetoric, which is designed to suggest that Reagan's election could increase the risk of war.

He predicted "a continual sobering among individual Americans" as Election Day approaches, and added:

"The personal characteristics of the candidates, as far as attractiveness or speaking style and so forth, in my opinion become less important and the questions come down to who cares more about me and my family and my future, who can deal with the inevitable crises in a more calm and effective way and who is most likely to keep this country at peace."