WASHINGTON, June 2 - U.S. Democratic presidential candidate Hillary Clinton lambasted Donald Trump's foreign policy platform as "dangerously incoherent" in a speech on Thursday that cast her Republican rival as both a frightening and laughable figure.

In remarks that at times resembled a comedy roast, Clinton unleashed a torrent of polished zingers and one-liners to attack Trump's policies and character, suggesting Trump might start a nuclear war if elected to the White House simply because "somebody got under his very thin skin."

"Donald Trump's ideas are not just different, they are dangerously incoherent," she said to a room of supporters in San Diego, California. "They're not even really ideas, just a series of bizarre rants, personal feuds and outright lies."

Clinton, the front-runner in the race to become the Democratic presidential nominee, delivered her speech as she seeks to shift her attention to the Nov. 8 election against likely rival Trump and away from Bernie Sanders, a U.S. senator from Vermont, who is continuing his long-shot bid for the nomination.

Clinton was speaking in San Diego ahead of California's June 7 primary election.

Democratic Party leaders have fretted about how to best oppose Trump, who managed to knock out all 16 rivals for the Republican nomination in part with his uninhibited style of assailing them with personal insults. Trump revels in referring to Clinton as "Crooked Hillary" and dredging up the infidelities of her husband, Bill Clinton, the former president.

Clinton's remarks were intended in part to show she would not be cowed and that she could go toe-to-toe with him in scornful put-downs.

"He says he has foreign policy experience because he ran the Miss Universe pageant in Russia," she said as the crowd guffawed, and she suggested Trump would run the U.S. economy "like one of his casinos."

During her speech, Clinton predicted Trump, who has been deeply critical of Clinton's foreign policy record, would take to his Twitter account to insult her, and he did.

"Bad performance by Crooked Hillary Clinton!" ran one posting during the speech, which included a typo. "Reading poorly from the telepromter! She doesn't even look presidential!"

Trump has said previously that Clinton is distorting his actual policies.

Two visions

Amid the laugh lines, Clinton cited her own experience as secretary of state, in particular her role advising President Barack Obama during the mission to kill al Qaeda leader Osama bin Laden, to suggest her approach to foreign policy was the more serious.

"He praises [people] like Vladimir Putin and picks fights with our friends, including the British prime minister, the mayor of London, the German chancellor, the president of Mexico and the pope," Clinton said, listing some of the allies with whom Trump has verbally sparred in the last year.

Obama, who has also been repeatedly mocked by Trump, has criticized Trump as being ignorant or cavalier about world affairs and has said that Trump's rise has "rattled" foreign leaders.

Trump has talked tough on foreign policy. He has said he would bring back waterboarding and other brutal interrogation techniques for terrorism suspects that are widely regarded as torture and were discontinued by Obama.

Trump has also vowed to renegotiate trade deals, called for a temporary ban on Muslims entering the country, and said he would ask members of the 28-nation NATO alliance to "pay up" or "get out." He has said he would sit down with North Korean leader Kim Jong Un to try to stop Pyongyang's nuclear program.

Clinton derided these and other positions, promising she would do a better job keeping the United States safe. Standing in front of a backdrop of 19 large U.S. flags, an unusual abundance even by the standards of presidential campaign events, Clinton painted the election as a choice between "two very different visions."

"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.