"That will be short-term popular. If you remember Bush, Bush was unbeatable for about two months, and then all of a sudden the world set in when he attacked Iraq. And he went from very popular to not popular at all. I think that Obama will start in some form a war with Iran, and I think that will make him very popular for a short period of time," Trump said.

The real-estate mogul went on to predict that a conflict "will make him hard to beat," presumably in the November election.

Tensions with Iran have intensified over Tehran's nuclear weapons testing program, with many in the United States and Israel expressing concern. But in a March press conference, the president pushed back against conservative calls for military action, arguing that the dispute should be solved through diplomacy and sanctions rather than military action.

"When I see the casualness with which some of these folks talk about war, I’m reminded of the costs involved in war. I’m reminded of the decision that I have to make, in terms of sending our young men and women into battle, and the impacts that has on their lives, the impact it has on our national security, the impact it has on our economy," Obama told reporters.

"This is not a game, and there’s nothing casual about it. And, you know, when I see some of these folks who had a lot of bluster and a lot of big talk, but when you actually ask them, specifically, what they would do, it turns out they repeat the things that we’ve been doing over the last three years. It indicates to me that that’s more about politics than actually trying to solve a difficult problem."

Trump — who notably endorsed GOP frontrunner Romney earlier this year and has campaigned vocally on behalf of the former Massachusetts governor — also agreed that his preferred candidate needed to loosen up on the campaign trail.

"If he just would be himself, and maybe stop listening to all of the geniuses that surround him, I think this guy has got the greatest way, the greatest manner and the greatest personality," Trump said.