Former Vice President Joe Biden and his aides have lined up hosts for his two-day Bay Area fundraising tour, including a former Twitter executive and veteran Democratic financiers, CNBC has learned.

Starting June 28, Biden will be traveling to San Francisco to take part in a fundraising event at the home of former Obama and Clinton bundler Doug Hickey, according to people with direct knowledge of the planning.

Hickey, a businessman, also served as President Barack Obama's commissioner general of the USA Pavilion in Italy. He helped raise up to $200,000 for Obama's 2008 run, according to the nonpartisan Center for Responsive Politics. He also bundled for Hillary Clinton when she ran for president in 2016.

Biden will also head to a another June 28 gathering, hosted by philanthropist and party financier Leni Eccles in Marin County, these people added. She raised $500,000 for Obama during his 2012 reelection campaign and helped Clinton four years later.

The next day, Biden will go to an event with former Twitter executive Katie Stanton in Silicon Valley, according to people with knowledge of the planning. Stanton is a veteran of the Obama administration, which she joined in 2009 after a tenure as a Google executive. She also served as an advisor to the State Department when Clinton was in charge there. She's currently a founding partner of an investment collective titled #ANGELS. Its website says it focuses on start-ups that are often led by women.

The tickets for the fundraisers that weekend are priced at up to $2,800, and the events are close to full capacity. CNBC first reported on Biden's allies preparing for him to come to Northern California at the end of June. A fundraiser in nearby Sonoma is being planned for late 2019.

The Biden campaign, Eccles and Stanton did not return requests for comment. Hickey could not be reached.

Biden's Bay Area fundraising blitz comes as he crisscrosses the country, vying for campaign cash as he and his 22 rivals in the Democratic primary field look to end the quarter on a strong note. All campaigns must close their books by June 30, the day after Biden's last event in Silicon Valley. Before he makes his way to the West Coast, the former vice president will be in New York for a gathering hosted by short selling investor Jim Chanos with Gov. Andrew Cuomo as the special guest.

Even though this would mark Biden's first trip to San Francisco since he announced his run for president, other campaigns have already planted their flags in the area. South Bend, Indiana, Mayor Pete Buttigieg has taken part in numerous fundraising events there, as has Sen. Kamala Harris, who previously served as the city's district attorney.

Biden's travels to California at the end of the month will likely come under scrutiny after he did not attend California's state Democratic Party convention earlier this month in San Francisco.

Sen. Bernie Sanders' speechwriter David Sirota blasted Biden for appearing to make the campaign donor events a priority over the convention.

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Biden's rivals at the event seized on his absence. "There is a debate among presidential candidates who have spoken to you here in this room and those who have chosen for whatever reason not to be in this room about the best way forward," Sanders said at the time.

The controversy didn't deter key Biden aides from heading to San Francisco earlier this month for a meeting with confidants to discuss their fundraising strategies and how much they've raised so far.