WASHINGTON, Aug. 24 (Xinhua) -- U.S. President Donald Trump gave a rally-style speech in Charlotte, North Carolina on Monday afternoon after delegates formally nominated him for reelection at the 2020 Republican National Convention (RNC).

Inside a ballroom of the Charlotte Convention Center during the previously unannounced trip, Trump touted achievements of his first term, defended handling of the coronavirus pandemic, complained about media coverage of the RNC, and railed on Democrats as well as the party's 2020 presidential nominee and former U.S. Vice President Joe Biden.

Trump said the United States is "doing very, very well" against the coronavirus, which has infected more than 5.7 million people in the country, with roughly 177,000 deaths. His approval rate on the handling of the pandemic has dropped to 31 percent, according to the latest poll from the Associated Press-NORC Center for Public Affairs Research.

Additionally, he again argued that expanding access to mail-in ballots could invite massive fraud, a claim that experts say is not substantiated, as many states are set to allow voters to take part in the November election by mail amid the pandemic.

"What they're doing is using COVID to steal an election," Trump said, referring to Democrats' support of mail-in voting. "They're using COVID to defraud the American people, all of our people, of a fair and free election. We can't do that."

Biden, who formally accepted the Democratic Party's presidential nomination on the final night of its virtually-held convention last week, leads Trump by 7.6 percentage points nationally, according to the RealClearPolitics polling average. Trump, however, has repeatedly dismissed polls showing him falling behind.

In his Monday speech that lasted about an hour, Trump also touched on his policy priorities for the second term, including creating jobs, cutting taxes, lowering drug prices, strengthening law enforcement, curbing illegal immigration, continuing the military buildup, and sticking to the "American First" foreign policy.

The Charlotte convention, once expected to draw tens of thousands of people to the city, was forced to dramatically shrink after the coronavirus pandemic hit.

Just 336 delegates gathered at the convention venue, six from each state and territory, for the state-by-state roll call that formally nominated Trump and Vice President Mike Pence for the 2020 Republican presidential ticket. The delegates received tests and temperature checks and were instructed to wear a mask and practice social distancing.

"I felt an obligation to come to North Carolina," said Trump, who has wanted to use in-person activities to reboot his campaign. "It's a place that has been very good to me." Pence also addressed the convention. He and Trump were on official White House trips to "The Tar Heel State" on Monday.

The nomination was part of the four-day RNC themed "Honoring the Great American Story," with each night having a sub-theme. On Monday, it is "Land of Promise," which a Trump campaign official said honors "the promises President Donald J. Trump has kept since his first presidential campaign."

Speakers for the RNC's opening night will include former U.S. Ambassador to the United Nations Nikki Haley, Senator Tim Scott of South Carolina, and the president's eldest son, Donald Trump Jr.

Trump will deliver an acceptance speech on Thursday night from the White House South Lawn. On Wednesday night, Pence will deliver his acceptance speech at Fort McHenry in Baltimore, Maryland.

Republicans and others opposing Trump are holding "Convention on Founding Principles" in Charlotte this week, a gathering that organizers claimed would be an alternative to the RNC.

More than two dozen former Republican members of Congress, including former Senator Jeff Flake of Arizona, endorsed Biden for president on Monday.

"Today, given what we have experienced over the past four years, it's not enough just to register our disapproval of the president," Flake said in a live video on several social media platforms explaining his decision. "We need to elect someone else in his place - someone who will stop the chaos and reverse the damage."