The former secretary of state, who has repeatedly called Trump a "loose cannon," will seek today to contrast her foreign policy experience with Trump's.
Foreign policy adviser Jake Sullivan said Clinton would make clear how high the stakes are in the race, as well as share her "larger vision of who we are, what we're all about as a country."
"She is going to make clear why Donald Trump is simply unqualified to be commander in chief," Sullivan said, adding that the speech "will go into specifics in a very direct and clear way about what makes Donald Trump unfit, both in terms of temperament and ideas. This is as full-throated and full-bodied a case as you will have seen from anyone on the danger that Donald Trump poses."
Trump accused Clinton of lying about his foreign policy plans at a rally at an airport hangar in Sacramento, California, last night.
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"She lies. She made a speech and she's making another one tomorrow. And they sent me a copy of the speech and it was such lies about my foreign policy," Trump said.
Trump has suggested in the past that he might be OK with Japan one day obtaining nuclear weapons.
Clinton's campaign hopes her foreign policy experience will appeal to voters who may be wary of Trump's bombastic style and lack of international experience. They hope those points, combined with Trump's controversial statements about women and minorities, will give Clinton opportunities with independent and moderate Republican voters.
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Clinton said Trump spends all his time in denigrating and criticising America. She added that the billionaire from New York has "insulted a huge majority" of American people during his campaign.
"You see, I am very excited about the future. And every election is about the future. In fact, there is such a difference in our visions for the future. I have a positive, optimistic, unified vision of where America is going. When I listen to Donald Trump's dark and divisive vision, I sometimes don't know what country he's talking about," she said at an election rally here attended by several thousand people.
"When I think about all of the people that Donald Trump has insulted in this campaign, literally, he has insulted a huge majority of the American people. I mean, think about it. He started with immigrants, moved on to Latinos, African Americans, Muslims, people with disabilities, prisoners of war, and then women. I mean, think about it," she said.
At a rally in Florida earlier, Clinton said "we should be build up their self-worth so that any young person in America can say they're going after their piece of the American dream - because the American dream is big enough for everybody".
"Now, we know what the tape about Donald Trump said. We know that he said some terrible things about what he does to women. I'm not going to repeat it. But bragging about treating women like that is not the message we want either our little girls or our little boys to hear," she said.
Highlighting a recent report that found Trump's means of avoiding federal income taxes "legally dubious", she called on Trump to release his tax returns so the Americans "finally see the truth" about his foreign and domestic entanglements, and contributions to the military, schools and infrastructure.
At the election rally in Dade City, Clinton highlighted Trump's alarming words and deeds towards women like his revolting comments on a bus 11 years ago, his repeated behaviour insulting and degrading women who stood up to him, his bragging about walking in on nude pageant contestants - some of whom were apparently underaged, his jokes that objectify women and more.