"I'll endorse, but I'm not a part of the campaign," Giuliani told CNN's Chris Cuomo on "New Day."
When pressed by Cuomo to clarify what he meant, Giuliani repeated that he would endorse Trump, but not have a role on the campaign.
"I'm Rudy Giuliani, I mean a lot in New York politics, I endorse Donald Trump, but I'm not a part of the campaign," the former mayor said. "I'm not a part of the campaign apparatus and I don't want people to think I am."
Giuliani explained some more of his thinking later Tuesday, saying he thinks Hillary Clinton would easily dispatch with Ted Cruz in a general election but have no idea how to handle Trump.
"Cruz is what we throw at them all the time -- a hard-right Republican. It's a fastball down the middle of the plate and Hillary Clinton has a playbook for hitting that out of the ballpark," Giuliani told CNN's Jake Tapper on "The Lead." "She doesn't know what Donald Trump is gonna throw at her. I don't know what Donald Trump is going to throw at her."
Asked about Ohio Gov. John Kasich, Giuliani flatly dismissed him, arguing that he wasn't a candidate anymore.
"Kasich isn't even a candidate -- he's not if you stick by the rules," Giuliani said, playing on the Trump argument that convention rules are already in place and thus block Kasich from being considered.
However, the rules for the Republican convention in Cleveland have not been written yet, and the question of whether to block Kasich using a measure from the 2012 convention is being hotly debated behind the scenes.
Giuliani's support for Trump has been just under 100% before. Giuliani has dodged formally endorsing the New York real estate tycoon in the past. When pressed by Fox News Monday night why he would not endorse the Trump, Giuliani said that an endorsement implies having a campaign role.
"The New York Post endorsed Donald Trump. I don't think anybody thinks The New York Post is part of the campaign."
"I'm voting for him, I'll do whatever they would like me to do, but I'm not part of the campaign apparatus, I don't speak for the campaign," Giuliani had told Cuomo on "New Day." "When I endorse somebody, I join their campaign. I join their campaign staff. Their campaign staff sends me out to do speeches, to do things like that. Donald's a very, very good friend, I believe he'd be the best candidate. I think he'd be the person I would like to see win."
Asked if he had concerns about the campaign, he said "sure." Giuliani had said he agreed with Trump on "eight out of 10 positions, and that's probably good enough for me. That's what I agreed with Ronald Reagan on, and he was my hero. But I have a couple of concerns on immigration. There are things I'd have to talk out first as far as an endorsement."