President Trump said in an interview aired Sunday that the rising number of U.S. deaths from the coronavirus “is what it is,” defended his fumbled management of the pandemic with a barrage of dubious and false claims, and revealed his lack of understanding about the fundamental science of how the virus spreads and infects people.

Making one of his biggest media appearances in months — an hour-long, sit-down interview with “Fox News Sunday” anchor Chris Wallace — Trump was visibly rattled and at times hostile as he struggled to answer for his administration’s failure to contain the coronavirus, which has claimed more than 137,000 lives in the United States.

On a range of other topics, including the racial justice movement and the Confederate flag, the president positioned himself firmly outside the political mainstream. And Trump suggested he might not accept the results of November’s general election should he lose because he predicted without evidence that “mail-in voting is going to rig the election.”

In a season of remarkable public appearances by a politically wounded president, the Wallace interview was still extraordinary, in part because of the volley of false claims by Trump and aggressive, real-time fact-checking by his questioner.

Trump — who aides say no longer attends coronavirus task force meetings because he does not have time — showed himself to be particularly misinformed about the basics of the virus that has been ravaging the nation for more than four months.

Confronted by Wallace with a chart showing that the number of coronavirus cases last week more than doubled from the spring peak in April, Trump replied: “If we didn’t test, you wouldn’t be able to show that chart. If we tested half as much, those numbers would be down.”

By the president’s logic, that assumes people contract the virus only if they test positive, ignoring the fact that many people are asymptomatic carriers and unknowingly spread the contagion without taking a test or being reported.

Wallace later explained to Trump that the number of tests has increased by 37 percent but the number of cases has shot up by 194 percent. Trump replied, “Many of those cases are young people that would heal in a day. They have the sniffles and we put it down as a test. Many of them — don’t forget, I guess it’s like 99.7 percent, people are going to get better and [in] many cases, they’re going to get better very quickly.”

Though people in their 20s and 30s, who make up a growing proportion of cases, have been hospitalized at a lower rate than older people, many still have suffered severe illness and some have died.

Former vice president Joe Biden, the presumptive Democratic presidential nominee, reacted to Trump’s interview in a statement Sunday: “The past six months have proven again and again that it’s Donald Trump who doesn’t know what he’s talking about when it comes to COVID-19 . . . When it comes to the coronavirus, you can’t believe a word he says.”

A growing number of Americans disapprove of Trump’s handling of the pandemic. A new Washington Post-ABC News poll found 38 percent approve of his performance and 60 percent disapprove. The same survey found Biden leading Trump by double digits nationally, 55 percent to 40 percent.

In an attempt to regain their political footing, Trump and his aides recently have sought to divert attention from the soaring number of coronavirus cases by focusing on the rate of deaths. In the Fox interview, Trump falsely asserted, “I think we have one of the lowest mortality rates in the world.”

“It’s not true, sir,” Wallace replied. “We had 900 deaths on a single day just this week.”

Trump shouted to aides hovering nearby: “Can you please get the mortality rates?” White House press secretary Kayleigh McEnany quickly presented Trump with data she said was from Deborah Birx, a physician and the White House coronavirus response coordinator, backing up his claim.

“Number one low mortality fatality rates,” Trump claimed.

At that point, Fox interrupted the taped interview for Wallace to explain to his viewers that according to data from Johns Hopkins University, the United States ranked seventh among 20 countries in mortality rate, worse than Brazil and Russia. The White House relied on European data showing Italy and Spain doing worse than the United States but Brazil and South Korea doing better. The White House chart did not include Russia and other countries doing better, according to Wallace.

When Wallace pointed out that coronavirus deaths in the United States were still about 1,000 a day, Trump said: “It came from China. They should’ve never let it escape, they should’ve never let it out, but it is what it is.”

Trump then hypothesized that the case count in Europe was so much lower than in the United States because “they don’t test,” as opposed to a sign that the virus was not as rampant there because their countries had largely contained it.

By conducting mass testing, Trump said, “We are creating trouble for the fake news to come along and say, ‘Oh, we have more cases.’ ”

Trump reiterated his long-held theory that the virus would somehow “disappear,” a claim not grounded in scientific fact.

“I will be right eventually,” Trump told Wallace. “You know I said, ‘It’s going to disappear.’ I’ll say it again. It’s going to disappear, and I’ll be right . . . You know why? Because I’ve been right probably more than anybody else.”

Trump used his Fox interview to continue the White House’s remarkable assault on some of the scientists and public health professionals spearheading the government’s response. The president called Anthony S. Fauci, the nation’s top infectious-disease expert, “a little bit of an alarmist.” He noted that Fauci had argued internally against restricting travel from China, which Trump ordered in late January, and had initially said all Americans did not need to wear masks, before there was scientific evidence that doing so would help slow the spread.

Trump also challenged the assessment of Robert Redfield, director of the Centers for Disease Control and Prevention, who again warned last week that the pandemic could worsen this fall when flu season begins, reflecting widespread scientific consensus. “I don’t think he knows,” Trump said of Redfield.

Trump sought to draw a hard line on the coronavirus relief bill, saying it must include a payroll tax cut and liability protections for businesses, as lawmakers prepare to plunge into negotiations over unemployment benefits and other key provisions in coming days. Republican leaders are largely dismissive of the idea of cutting payroll taxes, which fund Social Security, while siding with Trump on the liability issue.

The Fox interview was conducted outdoors on a White House patio on an oppressively hot day — the president’s choice, as Wallace twice noted. Trump joked that he wanted to see Wallace sweat, but it was the president’s face that glistened with sweat as the Fox anchor engaged him on a wide range of other topics, including the race and justice issues that convulsed the country. Trump declined to say whether he found the Confederate flag offensive and defended what many Americans view as a symbol of slavery, racial oppression and treason.

“When people proudly have their Confederate flags, they’re not talking about racism,” Trump said. “They love their flag. It represents the South. They like the South. People right now like the South.”

Wallace followed up: “So you’re not offended by it?”

“Well, I’m not offended either by Black Lives Matter,” Trump replied. “That’s freedom of speech. You know, the whole thing with cancel culture, we can’t cancel our whole history. We can’t forget that the North and the South fought. We have to remember that, otherwise we’ll end up fighting again.”

Trump also teased the possibility that he might not accept the election results if he were to lose, jeopardizing America’s tradition of a peaceful transfer of power between presidents.

When Wallace asked Trump whether he considers himself a “good” or “gracious” loser, the president replied that he doesn’t like to lose. Then he added, “You don’t know until you see. It depends. I think mail-in voting is going to rig the election. I really do.”

For weeks now, Trump has claimed without evidence that the rise in voting by mail in many states makes voting susceptible to widespread fraud.

“Are you suggesting that you might not accept the results of the election?” Wallace asked.

“No,” Trump responded. “I have to see.”

Later in the interview, pressed on whether he will accept the results, Trump again declined to say. “I have to see,” he said.

Biden campaign spokesman Andrew Bates responded to Trump’s remarks in a statement: “The American people will decide this election. And the United States government is perfectly capable of escorting trespassers out of the White House.”

Trump sought to portray Biden as mentally vacant, telling Wallace that he did not want to characterize his opponent as “senile” but positing that “Joe doesn’t know he’s alive” and is “mentally shot.”

Trump then challenged Biden to a cognitive test, which the president characterized as exceedingly difficult. During a physical exam in 2018, Trump took the Montreal Cognitive Assessment — which includes animal pictures and other simple queries aimed at detecting mild cognitive impairment such as dementia — and has regularly boasted about it since.

Wallace told Trump that he tried the test himself after hearing the president brag about passing it. Wallace said “it’s not the hardest test,” adding that one of the questions on the version he took was to properly identify a picture of an elephant.

“I’ll bet you couldn’t even answer the last five questions,” Trump said. “I’ll bet you couldn’t. They get very hard, the last five questions.”

“Well, one of them was count back from 100 by seven,” Wallace said, adding: “Ninety-three.”