US Defense Secretary Mark Esper on Sunday said he did not see specific evidence from intelligence officials that Iran was planning to attack four US embassies, an assertion made by President Donald Trump in justifying the killing of Iran's top general.

While Esper said he agreed with Trump that additional attacks against US embassies were likely, he said on CBS's "Face the Nation" that Trump's remarks to Fox News were not based on specific evidence on an attack on four embassies.

"What the president said was that there probably could be additional attacks against embassies. I shared that view," Esper said. "The president didn't cite a specific piece of evidence."

When pressed on whether intelligence officers offered concrete evidence on that point he said: "I didn't see one with regards to four embassies."

Since confirming that Iranian military leader Qassem Soleimani had been killed by a US airstrike in Baghdad, administration officials have claimed they acted because of an imminent risk of attacks on American diplomats and service members in Iraq and throughout the region.

Democrats and a few Republicans in Congress have questioned the justification of the attacks and said they have not been given adequate, detailed briefings.

Trump said on Friday Iran probably had targeted the US embassy in Baghdad and was aiming to attack four US embassies before Soleimani was killed in a US drone strike on Jan. 3.

“We will tell you probably it was going to be the embassy in Baghdad,” Trump said in a clip of an interview on Fox News. “I can reveal that I believe it would have been four embassies.”

Esper said in a separate interview on CNN's "State of the Union" that the administration had "exquisite intelligence" that a broader attack against multiple embassies was likely but that could only be shared with the "Gang of Eight," a group of top congressional leaders who get briefed on sensitive information that the rest of Congress does not have access to.

National Security Adviser Robert O'Brien echoed Esper's comment that the administration had "exquisite intelligence" on NBC's "Meet the Press" that a threat was imminent but did not comment on evidence saying four embassies were targeted.

House Intelligence Committee chairperson Adam Schiff, a California Democrat and member of the Gang of Eight, said on Sunday that the group was not informed about possible attacks on four embassies.

"There was no discussion in the Gang of Eight briefings that these are the four embassies that are being targeted and we have exquisite intelligence that shows these are the specific targets," he said.

Republican senator Mike Lee on Sunday said he was worried about the integrity of information the president and security briefers have provided Congress about Iran.

"We were given somewhat general statements, and I believe that the briefers and the president believe they had a basis for concluding there was an imminent attack. I don't doubt that. It is just frustrating to be told that and to not get the details behind it," he said on CNN.