Before the announcement the event wouldn't take place, a handful of intense verbal clashes took place between Trump supporters and protesters as the crowd waited for his arrival. At a rally, on Saturday, Mr. Trump referred to Mr Sanders as "our communist friend".
A Trump rally scheduled for Sunday in Cincinnati, Ohio has also been cancelled, with the local spokesman for the campaign telling USA media that Secret Service supporting the campaign could not complete preparation work in time. Chicago police said five people were arrested.
Additionally, reporter Michelle Fields of the conservative news site Breitbart has alleged she was assaulted at a Trump press conference by someone who was ID'd by a Washington Post reporter as Trump's campaign manager Corey Lewandowski.
As Trump attempts to unify a fractured Republican Party ahead of Tuesday's slate of winner-take-all primary elections, the confrontations between his legion of loyal supporters and protesters who accuse him of stoking racial hatred have become increasingly contentious, underscoring concerns about the divisive nature of his candidacy. "I feel like they feel empowered to do whatever they want to do". And Rubio said, "You don't have the right to disrupt an event just because you disagree with someone".
Sanders says on ABC's "This Week" that anyone following Trump's campaign "knows that he tells the truth very, very rarely" and that in this instance, "He's lying again". A few minutes later Trump continued with his speech.
Trump earlier told the crowd the protests that forced him to postpone a rally in Chicago on Friday was a "planned attack" that "came out of nowhere".
On Saturday, Kasich and Rubio expressed reservations about upholding their pledge to support Trump should he win the nomination, one they reiterated at Thursday night's GOP debate.
In statements to the press, candidates Ted Cruz and Marco Rubio both described the incident as "sad" and said the people who chanted anti-Trump slogans and fought with Trump's fans inside a stadium at the University of IL should have respected the candidate and let the rally happen.
"What this campaign is about is bringing our people together, not letting Donald Trump or anybody else divide us up", Sanders said.
Trump said of conservatives: "We are treated so unfairly, and I'm treated very unfairly".
And you have to understand; they want me to tell my people, please be nice, be nice.
Candidate John Kasich, also a Republican, said that "the seeds of division that Donald Trump has been showing this whole campaign finally bore fruit, and it was ugly".
They showed great restraint. "Bernie!" at Donald Trump's postponed rally in Chicago.
"To be clear, I don't think the police reaction was appropriate to anyone involved, but most especially, to the people you can tell are clearly being peaceful and non-combative", Stokes said.
He said there was "so much anger" at the rally, adding: "I don't think it's directed at me, it's just something that's been going on for years".