Trump has previously called the non-endorsements from his former primary opponents "disgraceful," citing the pledge the candidates—including Trump—took.
"They signed a pledge saying they will abide, saying they will back the candidate of the party. And now they sit back," Trump said at a rally in Bangor, Maine at the end of July. "They broke their word. In my opinion, they should never be allowed to run for public office again. Because what they did is disgraceful."
Kasich has repeatedly refused to to endorse Trump, and said in an interview that aired Sunday with "Meet the Press" that he was ruling out voting for Clinton and said "it's very, very likely I will not" vote for Trump.
The Ohio Governor was criticized for not attending the Republican National Convention in his home state.
"My actions have spoken louder than any words. And think about this: I want to know when anybody had a convention in their state when they were the governor who didn't go into the convention hall," Kasich said in an interview with CNN last month.