WASHINGTON -- Two top U.S. health officials on Sunday disputed a claim by U.S. President Donald Trump that federal data on COVID-19 cases and deaths in the United States is overblown, and both expressed optimism that the pace of vaccinations is picking up.

"The deaths are real deaths," Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, said on ABC News鈥 This Week, adding that jam-packed hospitals and stressed-out healthcare workers are "not fake. That鈥檚 real.鈥

Fauci and U.S. Surgeon General Jerome Adams, who appeared on CNN鈥檚 State of the Union, defended the accuracy of coronavirus data published by the U.S. Centers for Disease Control and Prevention after Trump attacked the agency鈥檚 tabulation methods.

鈥淭he number of cases and deaths of the China Virus is far exaggerated in the United States because of the @CDCgov鈥檚 ridiculous method of determination compared to other countries, many of whom report, purposely, very inaccurately and low,鈥 Trump wrote on Twitter.

Trump, a Republican who leaves office on Jan. 20 after losing a bid for a second term to Democrat Joe Biden, has frequently has downplayed the severity of the pandemic. He has also scorned and ignored federal recommendations for containing the spread.

More than 20 million people have been infected in the United States and nearly 347,000 have died 鈥 or one out of every 950 U.S. residents - since the virus first emerged in China in late 2019, according to the CDC.

鈥淔rom a public health perspective, I have no reason to doubt those numbers and I think people need to be very aware that it鈥檚 not just about the deaths,鈥 Adams said. 鈥淚t鈥檚 about the hospitalizations, the capacity.鈥

Fauci and Adams expressed optimism that the pace of vaccinating Americans against the virus is accelerating after a slow start. More than 4.2 million people have been inoculated since Dec. 14 with one of two vaccines, far short of the Trump administration鈥檚 goal of 20 million by the end of 2020.

鈥淲e wanted to get to 20 million, but some glimmer of hope is that in the last 72 hours, they鈥檝e gotten 1.2 million doses into peoples鈥 arms, which is an average of about 500,000 a day,鈥 Fauci said. 鈥淲e are not where we want to be. There鈥檚 no doubt about that. But I think we can get there.鈥 He said he believed that the number of daily vaccinations could be expanded to 1 million and called for "a real partnership" between the federal and state governments.