LAS VEGAS (Reuters) - President Joe Biden returns to the campaign trail on Tuesday in the battleground state of Nevada where he will address the NAACP national convention, a major gathering of Black voters, in his first political speech after the attempted assassination of former President Donald Trump.

After the shooting of Biden's Republican rival on Saturday, the Biden campaign immediately pulled its television ads, called off verbal attacks on the former president and focused instead on a message of unity.

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.

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 Blacks turned out heavily for Biden in 2020, polls have shown waning support for him among Black voters in this election.

Derrick Johnson, the NAACP president, told Reuters on Monday that he hopes Biden lays out a plan to help Black Americans who are struggling economically and who are fearful that their rights are under threat.

"People are concerned about the price of gas, price of bread, but they're also concerned with their growing knowledge around Project 2025," Johnson said, 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 might 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.

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.

(Reporting By Jarrett Renshaw and Nandita Bose, editing by Heather Timmons and Cynthia Osterman)

By Nandita Bose and Jarrett Renshaw