President Donald Trump on Wednesday rebuked Republican isolationists who have argued it’s not necessary to prevent Iran from obtaining a nuclear weapon, dismissing them as not being his true supporters.

“My supporters are for me. My supporters are America First and Make America Great Again,” Trump said from the Oval Office, in response to a question about the foreign policy debates between hawks and isolationists in the GOP base. “My supporters don’t want to see Iran have a nuclear weapon. … Very simple: If they think it’s OK for Iran to have a nuclear weapon, then they should oppose me.”

The president said he believes Iran would use a nuclear weapon if it had one.

“I don’t want to get involved either, but I’ve been saying for 20 years, maybe longer, that Iran cannot have a nuclear weapon,” Trump said. “I’ve been saying it for a long time, and I think they were a few weeks away from having one.”

He highlighted apparent logical inconsistencies in isolationists’ position on the issue.

“The problem is they get themselves into a thing: They don’t want them to have nuclear, but then they say, ‘Well, we don’t want to fight,’” Trump said. “Well, you’re going to have to make a choice because it’s possible that you’re going to have to fight for them not to have nuclear.”

Trump softened some of his previous criticism of Tucker Carlson, a prominent voice in isolationist circles whom the president had rebuked earlier this week for railing against U.S. support for Israel. He said that Carlson had called him to apologize.

Trump said he’d pressed Carlson on whether he would accept a nuclear-armed Iran, and said that Carlson “sort of didn’t like that. I said, ‘Well, if it’s OK with you, then you and I do have a difference,’ but it’s really not OK with him.”

“Therefore, you may have to fight and maybe it’ll end, and maybe it’ll end very quickly, but there’s no way that you can allow — whether you have to fight or not — you can have Iran to have a nuclear weapon, because the entire world will blow up,” Trump continued.

Trump said he planned to hold a meeting in the Situation Room on Wednesday afternoon to discuss the situation in the Middle East, but said he would delay a decision on striking Iran as long as possible.

“I like to make the final decision one second before it’s due,” he said. “With war, things change. It can go from one extreme to the other. War is very bad. There was no reason for this to be a war.”

The president said that the United States is the only country with the capabilities to destroy the deeply buried Fordow nuclear facility, but reiterated that he had not yet made the decision to do so.

Trump said that the success of Israel’s operations on their first night of bombing raids last week had made him more willing to consider possible U.S. involvement and strikes.

He also sent somewhat mixed messages on whether he’s open to continued talks with Iran.

“I had a great deal for them. They should have made that deal. Sixty days we talked about it, and in the end they decided not to do it. And now they wish they did it, and they want to meet,” Trump said. “It’s a little late to meet, but they want to meet and they want to come to the White House … so we’ll see. I may do that. It’s a shame, it could have been done the easy way.”

He said that he’s seeking “total complete victory” over Iran, in which it cannot have nuclear weapons.

“Iran was very close to signing what would have been a very good agreement for them and maybe that could still happen, I guess,” he said, adding that Iranian negotiators’ interest in visiting the White House is “a big statement, but it’s very late.”

Trump also noted that it may be difficult for Iranian negotiators to actually leave the country to visit the White House for negotiations.

The latest comments appeared somewhat less aggressive than Trump’s warnings the previous day that the U.S. could assassinate Iran’s supreme leader, Ayatollah Ali Khamenei.

Trump today was largely noncommittal on the issue of regime change in Iran saying, “Sure, anything could happen. That? That could happen.”