U.S. President Donald Trump on Saturday told thousands of cheering supporters he had asked U.S. officials to slow down testing for the novel coronavirus, calling it a "double-edged sword" that led to more cases being discovered. 

Trump said the United States had now tested 25 million people, far more than other countries. 

"When you do testing to that extent, you're gonna find more people you're gonna find more cases. So I said to my people slow the testing down, please," Trump told a campaign rally in Tulsa, Oklahoma, where many supporters were not wearing face masks. 

A White House official said Trump was joking about his call for a slowdown in testing. 

"He was obviously kidding. We are leading the world in testing and have conducted 25 million+ in testing," the official said. 

The event – which the White House promised would be flooded with up to 100,000 people, but actually did not fill the 19,000-seat arena where Trump spoke – has emerged as a flashpoint in the pandemic era. 

The Republican president is trailing Joe Biden, the presumptive Democratic presidential nominee, in polls ahead of the November election. Biden has hammered Trump for his response to the pandemic.

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Trump said the "radical fake news" media had not given him credit for doing what he called "a phenomenal job" responding to the outbreak – even as six members of his own Tulsa advance team tested positive for COVID-19. 

Several U.S. states are reporting troubling spikes in coronavirus infection rates, mainly in the South and West, as Trump addressed America's largest indoor gathering in months. 

Health experts say expanded diagnostic testing accounts for some, but not all, of the growth in cases. They also call it a key tool in fighting the spread of the disease, which had been detected in at least 2.23 million people across the United States and killed some 120,000 Americans as of Saturday. 

Addressing a less-than-full arena for his first political rally in months, Trump also criticized anti-racism protests sparked by the death of George Floyd, an African American who died in the custody of Minneapolis police. 

The president, who has encouraged a militaristic response to the demonstrations nationwide while taking criticism for not showing more empathy for the plight of Black Americans, criticized some of the protests. 

"The unhinged left-wing mob is trying to vandalize our history, desecrate our monuments – our beautiful monuments – tear down our statues and punish, cancel and persecute anyone who does not conform to their demands for absolute and total control. We're not conforming," Trump said. 

(With input from Reuters, AFP)