Vice President Kamala Harris will interview three top candidates - Minnesota Governor Tim Walz, U.S. Senator Mark Kelly of Arizona and Pennsylvania Governor Josh Shapiro - at her Washington, D.C., residence on Sunday ahead of a final decision on her running mate.

Harris is expected to announce her choice as early as Monday, ahead of her first public appearance with the vice presidential nominee on Tuesday in Philadelphia, Reuters was first to report. The Harris campaign is also planning a social media announcement featuring the duo, officials familiar with the arrangements told Reuters.

Harris met with her vetting team on Saturday, including former attorney general Eric Holder, whose law firm Covington & Burling LLP scrutinized the finances and background of potential running mates. Holder and his office made in-depth presentations on each of the finalists, according to sources familiar with the process.

She met Transportation Secretary Pete Buttigieg for 90 minutes on Friday and is also meeting candidates virtually, the sources said. Kentucky Gov. Andy Beshear and Illinois Gov. J.B. Pritzker are the other candidates in contention for the job.

The candidates will be informed on Monday night or Tuesday morning whether they were picked, the sources said.

The choice of a running mate is one of the most consequential decisions of Harris' political career, as she hastily pulls together a campaign to challenge Donald Trump in the Nov. 5 election after President Joe Biden dropped out of the race last month.

Her shortlist includes all white men with a record of winning over rural, white or independent voters.

Harris' decision also influences the future direction of the Democratic Party, elevating the chosen candidate to the front of the line for future presidential contests.

Shapiro, one of the top contenders, has faced sharp criticism from the left, especially progressive groups and pro-Palestinian activists, over his support for Israel and his handling of college protests sparked by the war in Gaza.

"There must be a policy correction on Gaza and there must be a pro-working class policy agenda, including a Black agenda," said Nina Turner, co-chair of Bernie Sanders' 2020 campaign and a fellow at The Institute on Race, Power and Political Economy, a progressive research group. "Picking Governor Shapiro as a running mate risks closing that door."

His handling of a sexual harassment complaint against a longtime top aide has also been questioned, and labor groups including the United Auto Workers (UAW) union, that recently endorsed Harris for president, have criticized him for calls to expand voucher programs that allow public tax dollars to flow to private schools.

Some labour groups have also criticized Kelly for not supporting proposed legislation they argue would boost union organizing.

Shawn Fain, president of the UAW, said that despite backing Harris for president, his 370,000-member union is not supporting Kelly or Shapiro as a potential running mate.

Walz has become a favourite of progressives and youth groups who enjoy his attacks on Trump.

At 60, Walz is just a year older than Harris, but critics say he looks much older, which could be a liability to a campaign that is rebounding from Biden's departure over concerns about his age.

Walz responded to this criticism on X, saying he looks the way he does because he was a high school teacher and "supervised the lunchroom for 20 years. You do not leave that job with a full head of hair. Trust me."