President Joe Biden promised Black voters on Tuesday that he was "all in" to seek reelection on Nov. 5 and assailed Donald Trump's record as president, in his first political speech since his Republican rival's attempted assassination.

Biden was greeted by chants of "four more years" as he spoke to the NAACP's annual convention in Las Vegas, a major gathering of Black voters.

Biden said he was grateful that Trump was not seriously hurt at a campaign rally in Pennsylvania on Saturday but roundly criticized him on a variety of fronts including his handling of the economy during the coronavirus pandemic.

"Let me say it again because Trump is lying like hell about it - Black unemployment hit a record low under the Biden-Harris administration," Biden said.

He scolded Trump for initially contending that former President Barack Obama was not an American citizen and for his reference to "Black jobs" at the Trump-Biden debate on June 27.

"I am all in," said Biden.

The attempt on Trump's life on Saturday prompted the Biden campaign to pull its television ads, call off verbal attacks on the former president and focus instead on a message of unity.

"Our politics got too heated," said Biden.

The campaign's strategy previously was to focus on tough criticism of Trump as a threat to U.S. democracy and to highlight his failure to admit his 2020 election loss and his felony convictions.

Now, it is trying to calibrate a less pugilistic message that still strikes a stark comparison between the two candidates.

The National Association for the Advancement of Colored People, the oldest and largest U.S. civil rights organization, represents a key constituency for the Democratic Party. While Black voters turned out heavily for Biden in 2020, polls have shown waning support for him from the constituency in this election.

"People are concerned about the price of gas, price of bread, but they're also concerned with their growing knowledge around Project 2025," Derrick Johnson, the NAACP president, told Reuters on Monday, referring to a set of conservative policy proposals that have become a lighting rod for Trump critics.

On Sunday, Biden used the formal setting of the White House Oval Office to ask Americans to lower the political temperature, recommit themselves to resolving their differences peacefully. He said the Nov. 5 presidential election will be a "time of testing."

In an interview with NBC News, Biden said on Monday it was a mistake for him to use the term "bullseye" in reference to Trump during a recent donor campaign call.

The president postponed a trip to Texas on Monday, where he was expected to speak on the 60th anniversary of the Civil Rights Act at the Lyndon B. Johnson presidential library.

White House officials hope the Trump assassination attempt will ease pressure on Biden to step aside as his Democratic Party's candidate in response to concerns about his mental acuity and stamina to govern for another four-year term.

At the end of his remarks in Las Vegas, Biden addressed the criticism that he is too old for the job.

“Hopefully today I’ve demonstrated a little bit of wisdom. Here’s what I do know. I know how to tell the truth. I know right from wrong. I know how to do this job. And I know the good Lord hasn’t brought us this far to leave us now. We have more work to do," he said.

On Wednesday, Biden is scheduled to speak to Latino leaders at the UnidosUS Annual Conference also in Las Vegas.

Meanwhile, Trump and Republicans are gathered in Milwaukee for the party's nominating convention that kicked off Monday with the selection of U.S. Senator J.D. Vance as Trump's running mate.