LAS VEGAS/MILWAUKEE — US President Joe Biden again faced calls to exit the presidential race as he tested positive for COVID-19 on Wednesday, while former president Donald Trump's running mate J.D. Vance formally accepted the Republican vice-presidential nomination.

Biden tested positive for COVID-19 while traveling Wednesday in Las Vegas and is experiencing "mild symptoms" including "general malaise" from the infection, the White House said.

Biden was scheduled to speak at a conference for the Latino civil rights and advocacy group UnidosUS, but he would no longer be able to attend. Biden previously tested positive in 2022.

The diagnosis came as Biden faces mounting pressure from some Democrats to step down from the presidential race due to concerns about his age and mental fitness following his poor debate performance against Trump in late June.

Prominent Democratic Representative Adam Schiff on Wednesday joined nearly 20 Congress members of his party to press Biden to withdraw from his reelection bid, as the Democratic National Committee grapples with uncertainties in the nomination process scheduled to be completed by the end of next month.

While the "choice to withdraw from the campaign is President Biden's alone", it is time for Biden "to pass the torch" and "secure his legacy of leadership" by allowing another Democrat to beat Trump, Schiff said in a statement.

US Senate Democratic leader Chuck Schumer told Biden in a meeting on Saturday it would be better for the country and the Democratic Party if he ended his reelection campaign, ABC News reported on Wednesday.

Across the United States, nearly two-thirds of Democrats and 70 percent of citizens said Biden should step aside and let his party nominate a different candidate, according to a latest Associated Press-NORC Center for Public Affairs Research poll.

The AP-NORC poll, conducted from July 11-15, also found that only about 3 in 10 Democrats are extremely or very confident that he has the mental capability to serve effectively as president, down slightly from 40 percent in an AP-NORC poll in February.

In response to Schiff's comments, the Biden campaign has pointed to what it called "extensive support" for him and his reelection bid from members of Congress in key swing states, as well as from the Congressional black and Hispanic caucuses.

The Democratic National Committee is pushing ahead with plans for a virtual vote to formally make Biden its nominee in the first week of August, before the Democratic convention scheduled for Aug 19-22 completes the nomination process.

Meanwhile, Vance urged voters to "choose a new path" as he formally accepted his nomination to be the Republican Party's vice-presidential candidate in an address on Wednesday.

"I stand here humbled, and I'm overwhelmed with gratitude to say I officially accept your nomination to be vice-president of the United States of America," he told the Republican National Convention in Milwaukee, Wisconsin.

Trump, who has just survived an assassination attempt, is set to formally accept his party's nomination with an address later on Thursday.

Hundreds of people attended a vigil to remember the former fire chief killed at a Trump rally in Pennsylvania.

In the face of security concerns aired after the shooting, Secret Service Director Kimberly Cheatle has agreed to testify before the House of Representatives Oversight Committee on July 22 for a hearing related to the shooting, the panel said on Wednesday.

US prosecutors formally appealed on Wednesday a federal judge's decision to throw out the criminal case brought by Special Counsel Jack Smith accusing Trump of illegally holding on to classified documents following the end of his presidency.

Smith's office filed a notice indicating it would ask the Atlanta-based 11th US Circuit Court of Appeals to revive the case and reverse Florida-based US District Judge Aileen Cannon's ruling on Monday that Smith had been unlawfully appointed by Attorney General Merrick Garland.

Agencies/Xinhua