President Donald Trump said Monday he'd like to help the Iranian people "if they can behave, but they've been very menacing."

"I'd love to help them, but they have to be in a system that allows them to be helped, and right now they're in a system that only allows failure. And I don't want that," he said when asked during a press briefing Monday about his intentions for helping Iranians once his military objectives are over.

"I want a system that's not going to be attacking us," he continued. "We want a system that can lead to many years of peace, and if we can't have that, we might as well get it over with right now."

President Donald Trump said he doesn't "know enough" about a deadly strike on an Iranian girls school when pressed on the incident during Monday's briefing.

The U.S. military was striking targets in Iran in an area where an elementary school was hit and dozens of children were killed on Feb. 28, sources told ABC News.

A newly surfaced video appears to show a U.S.-made missile hitting a building in Iran adjacent to the girls’ school where local officials say 168 people were killed, experts told ABC News.

Asked Monday if the U.S. will accept any responsibility for the strike, Trump said the missile is "very generic."

"I will say that the Tomahawk, which is one of the most powerful weapons around, is used by, you know, is sold and used by other countries," he said, adding that Iran "also has some Tomahawks."

Trump said the incident is being investigated.

"I just don't know enough about it," he said.

"Whatever the report shows, I'm willing to live with that report," he added.

President Donald Trump said he believes the war with Iran is "going to be ended soon."

"And if it starts up again, they'll be, they'll be hit even harder," he said of Iran during a press briefing on Monday.

Asked by a reporter what he means by "soon" and if he's thinking it will be over this week, he said, "No, but soon."

Trump was asked again by a reporter on the timeline of the Iran operation and how long should Americans expect, after Defense Secretary Pete Hegseth said on "60 Minutes" on Sunday that "this is only just the beginning" of the U.S. campaign.

Trump said it's the "beginning of building a new country" and that Iran has no navy or air force. 

"We could call it a tremendous success right now, as we leave here, I could call it, or we could go further, and we're going to go further," he said.

Secretary of State Marco Rubio held a call with Iraq's prime minister on Monday, according to the State Department.

During their conversation, Rubio "strongly condemned terrorist attacks by Iran" and its militia proxies in Iraq, including the Iraq Kurdistan region, according to the department's readout.

Both Rubio and Prime Minister Mohammed Shia al-Sudani "reiterated the importance" of the Iraqi government doing all it could to protect U.S. diplomatic personnel and facilities, according to the readout.

-ABC News' Shannon K. Kingston

As the war in Iran enters its third week, President Donald Trump told reporters on Air Force One Sunday night that he is talking to countries about policing the Strait of Hormuz, saying he is looking at “about seven,” but declined to give specifics on which countries they may be.

Trump also said that the Strait of Hormuz is “something that we don't need,” arguing that other countries should step in and assist because it affects them more than the U.S.

“I really am demanding that these countries come in and protect their own territory, because it is their territory. It's the place from which they get their energy, and they should come and they should help us protect it,” the president said.

Trump also suggested the U.S. not assist at all.

“You could make the case that maybe we shouldn't be there at all because we don't need it. We have a lot of oil people with the number one producer anywhere in the world,” he said.

-ABC News' Meghan Mistry and Emily Chang