Hillary Clinton has declared herself as the Democratic Party nominee for US president, saying she has made history as the first woman to lead a major party in a race for the White House.
The former first lady, senator and US secretary of state beat rival Bernie Sanders in New Jersey's nominating contest, expanding her lead a day after she captured the number of delegates needed to clinch the nomination.
"Together, we secured the Democratic nomination. For the first time ever, a woman will be a major party's nominee to become President of the United States," Ms Clinton, 68, wrote in a fundraising email to supporters on Tuesday (local time).
New Jersey was one of six states holding contests on Tuesday, including California, the big prize where Ms Clinton was still at risk of an embarrassing loss to Sanders as she heads into a campaign against presumptive Republican nominee Donald Trump in the November 8 election.
Mr Sanders, 74, was projected to win in North Dakota, and there were no immediate projections in Montana, New Mexico or South Dakota in the final series of big presidential nominating battles that began on February 1 in Iowa.
The District of Columbia, the last to vote, holds a Democratic primary next Tuesday.
In the fundraising email to supporters, Ms Clinton declared her campaign had broken "one of the highest, hardest glass ceilings".
"Tonight, we can say with pride that, in America, there is no barrier too great and no ceiling too high to break," Ms Clinton wrote on Twitter.
"To every little girl who dreams big: Yes, you can be anything you want - even president. Tonight is for you," she tweeted.
Ms Clinton's race against Trump, 69, will unfold as she faces an ongoing investigation of her use of a personal email server while Secretary of State. Opinion polls show the controversy has hurt Ms Clinton's ratings on honesty and trustworthiness.
Ms Clinton, who now must try to unify the party and win over Sanders supporters, was expected to highlight the historic nature of her nomination at an event in new York on Tuesday night.
Her campaign has compiled a video tying her to women's rights movements in American history.
She wants to move beyond the primary battle and turn her attention to Mr Trump. But Mr Sanders, a democratic socialist US senator from Vermont, has vowed to stay in until July's party convention that formally picks the nominee, defying growing pressure from party leaders to exit the race.
Although Mr Sanders will be unable to catch Ms Clinton even if he wins the primary in California, America's most populous state, a triumph there could fuel his continued presence in the race and underscore Ms Clinton's weaknesses as she heads into the fight with Mr Trump.
Polls in California were due to close at 11pm local time on Tuesday (3pm NZT Wednesday).
Mr Sanders was determined to stay in the race, even after the Associated Press and NBC reported on Monday night that Ms Clinton had clinched the number of delegates needed to win the nomination. A Sanders campaign spokesman castigated what he said was the media's "rush to judgment".
The delegate count also includes superdelegates, party leaders who can change their minds at any time. Ms Clinton's superdelegate support outnumbers Mr Sanders' by more than 10 to 1.
The Sanders' campaign has said it can still persuade superdelegates to switch to him, although in practice superdelegates who have announced their intentions are unlikely to change their minds.
Mr Sanders would have to get more than 60 percent of the superdelegates backing Ms Clinton to switch their votes.
So far, his campaign manager, Jeff Weaver, acknowledged they had yet to convert a single delegate.