US Democratic presidential candidate Hillary Clinton has taken quick aim at presumptive Republican nominee Donald Trump, saying the United States should not take a risk on an unreliable candidate.
"He is a loose cannon, and loose cannons tend to misfire," Clinton said in an interview with CNN on Wednesday (local time), citing Trump stances including a claim that climate change was a Chinese hoax.
Clinton, former secretary of state and the front-runner to win the Democratic nomination, said Trump needs to offer policy specifics in the general election on November 8 and criticised him for his positions on issues including nuclear weapons and abortion.
"He makes these grand statements and grand accusations," Clinton said of the real estate magnate and former reality TV star.
"At some point when you're running for president, you actually have to put a little meat on the bones.
"You've got to tell people what it is you're going to do and how you're going to do it."
Clinton lost the Democratic primary contest in Indiana on Tuesday but still looks set to win her party's nomination, leading her rival, US Senator Bernie Sanders, by more than 800 delegates.
Trump's Indiana win pushed his rivals out of the race, leaving him as the presumptive nominee.
In a preview of the likely general election battle to come, Clinton laughed when asked if she was ready to take on Trump, saying "Oh, please."
"This is to me a classic case of a blustering, bullying guy who has knocked out of the way all the Republicans because they were just dumbfounded," she said.
Clinton said she knows how to run a campaign against Trump and took a swipe at Trump's 16 Republican presidential rivals who started out in the 2016 campaign.
"They didn't know how to deal with him," Clinton said.
"They couldn't take him on the issues because they basically agreed with them. And they didn't know how to counterpunch."