U.S. Vice-President Kamala Harris on Friday secured the delegate votes needed to clinch the Democratic U.S. presidential nomination and become the first woman of colour at the top of a major party ticket.

Harris became the front-runner for the Democratic nomination after U.S. President Joe Biden bowed to pressure from within the party and dropped out of the race last month. Harris quickly won the support of party heavyweights and was the only candidate to qualify for the Democratic presidential ballot, which ensured the outcome of the delegate voting was never in doubt.

Party delegates voted virtually this week. Harris, who joined the livestream event where the announcement was made, said she would officially accept the nomination next week after the virtual voting period had closed.

"But already I'm happy to know that we have enough delegates to secure the nomination," said Harris, the first Black and South Asian person to become U.S. vice-president.

"And later this month, we will gather in Chicago united as one party where we're going to have an opportunity to celebrate this historic moment together."

Harris needed to pass a 2,350-vote threshold from delegates to formally secure the nomination, her campaign said.

Democratic leaders had pledged to deliver a presidential nominee by Aug. 7, before the Aug. 19-22 Democratic National Convention (DNC) in Chicago.

The DNC had said a virtual vote was needed to ensure the nomination process was completed by Aug. 7, the date by which Ohio law required a nominee in place to make the state's ballot.

Ohio lawmakers subsequently pushed back the deadline to Sept. 1, but party officials said they nevertheless wanted to meet the Aug. 7 deadline to avoid any legal risk in the state.