Trump says damage to Iran's nuclear sites is 'far below ground level'

President Donald Trump appeared to float the idea that there should be a change in leadership in Iran in a new social media post on Sunday. Trump said that though it is "not politically correct" to discuss a regime change, he criticized the current leadership in Iran and also asked, "Why wouldn’t there be a Regime change???"

"It’s not politically correct to use the term, “Regime Change,” but if the current Iranian Regime is unable to MAKE IRAN GREAT AGAIN, why wouldn’t there be a Regime change???," Trump wrote in the brief post on his social media platform, Truth Social.

"MIGA!!!," Trump added in the post, a twist on the MAGA term that he coined.

In an earlier post on Sunday, Trump touted the success of the U.S. strikes on Iranian nuclear sites.

"The damage to the Nuclear sites in Iran is said to be 'monumental.' The hits were hard and accurate," Trump wrote.

-ABC News' Michelle Stoddart

Former CIA officer, U.S. Deputy Assistant Secretary of Defense for the Middle East and ABC News contributor Michael "Mick" Mulroy estimates that the U.S. military operation “likely set back the Iranian nuclear weapons program 2-5 years,” based on the type and amount of munitions used, but told ABC News that the full battle damage assessment will give a more accurate determination.

“The question now is whether this ends this conflict, starts another or least escalates it. That seems to be largely up to Iran,” Mulroy added.

Another former senior U.S. official with direct knowledge of the planning of this strike says Mulroy's assessment is correct in that the U.S. strike likely only set Iran back "a limited number of years," but also says there are ways of extending that.

-ABC News' Selina Wang and Matt Gutman

Rep. Jim Himes, the ranking Democrat on the House Intelligence Committee, said it was too early to know the success of a series of U.S. attacks against Iran – calling the strikes a "massive gamble" on the part of President Donald Trump and citing past U.S. military action in the region.

"I mean, we've seen this movie before. Every conflict in the Middle East has its Senator Tom Cotton who promised us mushroom clouds," Himes told ABC News' "This Week" co-anchor Jonathan Karl.

"In the Iraq war, it was Condoleezza Rice promising us a mushroom cloud. And initially – and this is true of every one of these wars, in Libya ... in Iraq and Afghanistan – initially, things look pretty good," Himes continued. "Saddam Hussein is gone. Muammar Gaddafi is gone. The Afghan Taliban are gone. And then over time, we start to learn what the cost is: 4,400 Americans dead in Iraq. The Taliban back in power."

Himes said it's too soon to call the attacks on Iran’s nuclear facilities a success and cautioned against applauding them.

"But bottom line is we don't know, and if you look at the three conflicts I just mentioned, I would keep the optimism under the hat for a little while yet," he said.

Himes also said that he was "disturbed" by the fact that the strikes were undertaken without the approval of Congress, which he said holds the sole authority to declare war.

"There's not much ambiguity in the Constitution about who gets to approve these things," Himes said.

The president gave the final order to attack Iranian sites to Defense Secretary Pete Hegseth on Saturday, a senior administration official tells ABC News.

The president departed his Bedminster golf club Saturday afternoon and returned to the White House for a national security meeting, according to the official.

The official told ABC News that diplomatic efforts were made in the week leading up to the strike, mainly through the president's special envoy, Steve Witkoff.

As those efforts continued, the Pentagon simultaneously prepared the operation. By the end of the week, there was a growing belief among U.S. officials that Iran was not going to come to the table to reach a deal, according to sources.

President Trump was briefed daily on Israel's efforts and the operation itself as he decided whether to move forward, according to sources. He stayed in close contact with Hegseth while traveling to Bedminster, receiving updates until he made the final call.

-ABC News' Rachel Scott