WASHINGTON (NYTIMES) - Senator Elizabeth Warren, whose full-throated opposition to high-dollar fund-raising events was a central tenet of her presidential campaign, has agreed to host such a gathering of donors for Mr Joe Biden, the presumptive Democratic nominee, who is considering her to be his running mate.

The online event is set to take place on June 15, according to three people with knowledge of the plans, who spoke under condition of anonymity to share the details.

During her presidential run, Ms Warren explicitly vowed not to attend private fund-raisers or dial up rich donors.

A Massachusetts progressive, she championed tax increases on the wealthy and at times sharply criticised big-money contributors.

Ms Warren's spokesman declined to comment. Biden campaign officials did not respond to requests for comment.

Ms Warren built a network of high-dollar donors as a senator and used to attend fund-raising events, building up her own campaign war chest before she entered the Democratic presidential race.

But in late February 2019, as she sought to gain traction in online presidential fund-raising, especially among progressives whom Senator Bernie Sanders, a Vermont Independent, was also courting, she ruled out big-money events.

Ms Warren will now mine her old donor network to help Mr Biden as she manoeuvres to become his running mate, a position that she has said she would accept if asked.

While she remains ideologically to Mr Biden's left, Ms Warren has edged closer to some of his positions.

Ms Warren, a supporter of a single-payer "Medicare for All" system, has voiced support for a proposal more in line with Mr Biden's position of expanding the Affordable Care Act.

Mr Biden's other rivals have aided his fund-raising since he became the party's presumptive nominee.

Former mayor Pete Buttigieg of South Bend, Indiana, raised US$1 million (S$1.42 million) in an online fund-raiser on Friday.

Mr Buttigieg is scheduled to appear at more fund-raising events with Mr Biden next week, as is Senator Amy Klobuchar of Minnesota.

Senator Kamala Harris of California, businessman Andrew Yang and Senator Kirsten Gillibrand of New York, all former rivals, are set to appear at Biden fund-raising events in June.

Mr Sanders sent a fund-raising appeal for Mr Biden to his donor list, but declined to share his list with the Biden campaign.