"One that's angry, afraid and based on the idea that America is fundamentally weak and in decline," she said, summing up Trumpism. "The other is hopeful, generous and confident in the knowledge that America is great, just like we always have been."
Trump has criticized Clinton for her handling of foreign policy during her 2009-2013 stint as secretary of state, including the Sept. 11, 2012, attack by Islamist militants on a U.S. diplomatic facility in Benghazi, Libya, that killed the U.S. ambassador and three other Americans.
He cites Clinton's support for the war in Iraq, launched by former Republican President George W. Bush, as another example of her shortcomings.
Democratic challenger Sanders echoed Clinton's concerns about Trump after her speech, though he also criticized Clinton's foreign policy. "I agree ... that Donald Trump's foreign policy ideas are incredibly reckless and irresponsible," Sanders said in a statement.
In criticizing Clinton, Sanders cited her vote for the war in Iraq, calling it "the worst foreign policy blunder in modern American history," and said "she has been a proponent of regime change, as in Libya, without thinking through the consequences."
In assailing each other's suitability for the White House, Clinton and Trump are reflecting a negative voter mood ahead of next month's party conventions that will choose the presidential nominees.
Both Clinton and Trump are facing record-low favorability ratings. A Reuters/Ipsos poll taken Friday through Tuesday shows half of Trump supporters say the primary reason they are going to vote for him is "I don't want Hillary Clinton to win," while 41 percent of Clinton supporters cite their primary reason as not wanting Trump to win.