President Trump ripped former President Barack Obama during an appearance on Rush Limbaugh's talk show, telling the longtime radio host that "we're a lot safer now" that he's in the Oval Office.

“He [Iranian Gen. Qassem Soleimani] was their real military leader," Trump said Monday on The Rush Limbaugh Show. "He’s a terrorist. He was designated a terrorist by President Obama. And then Obama did nothing about it, except give them $150 billion, even more incredibly $1.8 billion in cash.”

Limbaugh then asked Trump what he thought of the Obama administration's policy in Iran.

"I don't think they had a purpose; I don't think they knew what was happening. Why did he give them $150 billion? Much of it going back into terror, and you look at what's happening. When I first came into office, I went to the Pentagon, and they showed me 18 sites of confliction, meaning conflict over there, and every one of them was started by Iran," Trump said.

Trump ordered airstrikes that killed Soleimani and Iraqi militia leader Abu Mahdi al Muhandis last week after thousands of Iranian-backed militants encircled the U.S. Embassy in Baghdad on New Year's Eve. Before that, Iran launched a series of attacks on American assets in Iraq, including the death of an American contractor.

Iran's Supreme Leader Ayatollah Ali Khamenei has vowed "revenge," and a top general said the nation has listed 32 potential American targets. Trump, in turn, threatened "massive retaliation" if the country attacks, including potentially hitting 52 Iranian cultural sites.

[Read more: 'They’ve lost their minds': Trump claims Democrats are using impeachment to 'affect the election illegally']