Donald Trump has waded into the debate over whether former Secretary of State Hillary Clinton is "qualified" to be president.

In a Sunday speech in New York, the Republican presidential candidate referred to the recent dust-up between Clinton and Sanders over whether each was qualified to be president.

"You saw what Bernie said? They're starting to get angry at each other," Trump said. "Bernie's saying she shouldn't be able to be in that position, because she's made so many bad decisions — she shouldn't even be able to be running for the position."

"And she has made bad, bad decisions. I look so forward to going after Hillary."

Last week, Sanders seemed to suggest he believed that Clinton was not qualified to be president. However, Sanders has since said he does, in fact, believe Clinton to be qualified.

During an interview that aired Sunday on CNN, Sanders said that while he believes that Clinton has the experience to be president, her initial support for the 2003 invasion of Iraq and her previous support for various international trade agreements raised red flags.

"I have my doubts about what kind of president she would make," Sanders told CNN host Jake Tapper.

Trump repeatedly brought up the Democratic contest over the weekend.

During his speech on Sunday, the real-estate magnate also drew parallels between Sanders' deficit of presidential delegates and Trump's own problems securing the 1,237 delegates needed to clinch the Republican nomination.

"Take a look at what's happening to Bernie. He wins, he wins, he wins, he wins, and I hear he doesn't have a chance," Trump said, referring to Sanders' recent string of Democratic primary and caucus victories. "This is a crooked system, folks."

"I'm not a fan of Bernie. I couldn't care less about Bernie. But he wins, like me."