WASHINGTON -- U.S. Vice-President Kamala Harris has secured the support of enough Democratic delegates to become her party's nominee against Republican Donald Trump, according to an Associated Press survey taken in the aftermath of President Joe Biden's decision to drop his bid for re-election.

Harris, who was endorsed by Biden minutes after he announced he would not accept the Democratic nomination, worked to quickly lock up the support of her party's donors, elected officials and other leaders.

However, the Associated Press is not calling Harris the new presumptive nominee. That's because the convention delegates are still free to vote for the candidate of their choice at the convention in August or if Democrats hold a virtual roll call ahead of that gathering in Chicago.

The AP survey is only an indication that she has the backing of more than the 1,976 delegates she'll need to win on a first ballot. But it also finds she's the overwhelming choice of her party to replace Biden at the top of the ticket, as no other candidate was named by a delegate contacted by AP.

By Monday night, Harris had the support of at least 2,214 delegates, according to the AP tally, enough to win the nomination on the first ballot.

Prompted by voter concerns about his fitness for office following his June 27 debate with Trump, and a revolt among party leaders and donors, Biden quit the race on Sunday. But the quick coalescing behind Harris marked an attempt by the party to put weeks of internecine drama over Biden's political future behind them and to unify behind the task of defeating Trump with just over 100 days until Election Day.

Kamala Harris

The AP tally is based on interviews with individual delegates, public statements from state parties, many of which have announced that their delegations are supporting Harris en masse, and public statements and endorsements from individual delegates.

Locking up the nomination was only the first item on the staggering political to-do list for Harris after learning of Biden's plans to leave the race Sunday morning on a call with the presiden. She must also pick a running mate and pivot a massive political operation that had been built to reelect Biden to boost her candidacy instead.

On Sunday afternoon, Biden's campaign formally changed its name to Harris for President, reflecting that she is inheriting his political operation of more than 1,000 staffers and war chest that stood at nearly US$96 million at the end of June. She added US$81 million to that total in the first 24 hours after Biden's endorsement, her campaign said -- a presidential fundraising record -- with contributions from more than 888,000 donors.

Harris, if elected, would be the first woman and first person of South Asian descent to be president.

Speaking to campaign staff in Wilmington, Delaware, Harris acknowledged the "rollercoaster" of the last several weeks, but expressed confidence in her new campaign team.

"It is my intention to go out and earn this nomination and to win," she said. She promised to "unite our Democratic party, to unite our nation, and to win this election."

The Democratic National Convention is scheduled to be held Aug. 19-22 in Chicago, but the party had announced it would hold a virtual roll call before in-person proceedings begin. The convention's rules committee is scheduled to meet this week to finalize its nomination process with a virtual vote as soon as Aug. 1, the party announced on Monday, with the process completed by Aug. 7.

"We can and will be both fast and fair as we execute this nomination," Jaime Harrison, the Democratic National Committee's chair, said on a conference call with reporters.

The party said the virtual roll call would feature multiple rounds of voting on nominees if multiple candidates meet the qualification threshold. To qualify, candidates must have the electronic signatures of 300 convention delegates.