President Donald Trump's aides thought he invented his claim that top military commander Qassem Soleimani had to be killed because four US embassies were under threat, The Daily Beast reported.

"There were definitely questions [at the time, internally] about whether he had just made it up on the spot," one White House official said, according to the news site.

Turns out Trump had jumped on a vague talking point at a security briefing about US embassies being "possible targets," and then turned it into a national-security issue.

The president told a January 9 rally that Soleimani had been "actively planning new attacks" on embassies. The day after, he told Fox News' Laura Ingraham four US embassies had been in danger.

This new report further muddies the Trump administration's shifting justifications for directing the Soleimani strike. Senate and House lawmakers are investigating.

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White House aides thought President Donald Trump may have fabricated evidence to justify the killing of top Iranian general Qassem Soleimani, The Daily Beast reported Monday.

Trump told supporters at a January 9 rally in Ohio that Soleimani had been "actively planning new attacks, and he was looking very seriously at our embassies." The next day, he told Fox News' Laura Ingraham "I believe it probably would've been four embassies."

But after Trump made the claim, his own staffers struggled to establish its origin, and believe in its validity, the news site said.

Worshippers chant slogans during Friday prayers ceremony in front of a banner showing Soleimani and Iraqi Shiite senior militia commander Abu Mahdi al-Muhandis, who were both killed in a US strike in January. Associated Press

"There were definitely questions [at the time, internally] about whether he had just made it up on the spot," one White House official said, according to the Beast.

Turns out their concern was warranted, as officials later found out Trump had taken a minor warning in a security briefing, and inflated it into a real national security threat, the Beast reported.

According to one of its sources, Trump was merely alerted to the embassies being "possible targets" for Iranian retribution, meaning they were not under bona fide threat.

When he heard the word "embassies", a source told the Beast, Trump lit up, and began grilling officials for more information.

In other words, Trump had "simply seized on a small part of what he'd heard in private briefings, exaggerated that aspect of the intelligence, then began sharing the inflated intel to the American public during his post-Soleimani victory lap," the news site wrote, paraphrasing information from three sources familiar with the matter.

Mourners holding posters of Soleimani at his funeral ceremony in Tehran on January 6, 2020. AP Photo/Ebrahim Noroozi

In the aftermath of the strike on Soleimani, US defense officials, White House aides, and intelligence officials have struggled to put out a cohesive line on why Soleimani was assassinated, and what pressing threats he had posed to the US.

Here are the shifting explanations:

January 2: The Pentagon called the Soleimani strike a "defensive" action.

The Pentagon called the Soleimani strike a "defensive" action. January 6: Gen. Mark Milley, the chairman of the Joint Chiefs of Staff, said Soleimani was "planning, coordinating, and synchronizing significant combat operations," according to CNN.

Gen. Mark Milley, the chairman of the Joint Chiefs of Staff, said Soleimani was "planning, coordinating, and synchronizing significant combat operations," according to CNN. January 10: Secretary of State Mike Pompeo said that Soleimani posed an "imminent" threat, but later said there was no time frame in which the attacks were expected to occur.

Secretary of State Mike Pompeo said that Soleimani posed an "imminent" threat, but later said there was no time frame in which the attacks were expected to occur. January 12: Defense Secretary Mark Esper told CBS "the president said that he believed that it probably could have been attacks against additional embassies," but that Esper himself "didn't see [a specific piece of evidence] with regard to four embassies."

The Senate Select Committee on Intelligence and the House Permanent Select Committee on Intelligence are investigating the strike, but have battled to get to the bottom of conflicting testimonies like those of Pompeo and Esper.