The State Department cancelled two briefings on the Trump administration's Iran strategy at the last moment on Wednesday, CNN reported.

Another schedule for a separate closed-door session for the Federal Bureau of Investigation (FBI) was also cancelled.

FBI officials had been about to brief a group of House lawmakers on counterintelligence issues, during the briefing that was added to the calendar late last week.

The Pentagon also scrapped a Thursday classified briefing on Iran.

A spokesperson for the Department of Defense Jonathan Hoffman told CNN that it was working to schedule a time to conduct the briefing. He also said that the postponement was not a unilateral Pentagon move.

Trump pushed the US and Iran to the brink of war earlier this month when he ordered a drone strike that assassinated general Soleimani in Baghdad. Iran later responded with a barrage of retaliatory missile strikes hitting a key airbase hosting American forces in Iraq.

Democratic Senator Chris Murphy suggested that the White House was behind the sudden cancellation of Wednesday's scheduled briefing.

The cancellations come as some lawmakers, particularly Democrats, continue to question the Trump administration’s justification for assassinating general Soleimani, and administration’s shifting explanations on the assassination.

Secretary of State Mike Pompeo said the assassination of general Soleimani was part of a “bigger strategy of deterrence,” a shift from President Trump's previous claim that the deadly drone strike was carried out to prevent an “imminent” attack.

Some lawmakers were also questioning Trump’s claims that the top Iranian commander was planning “imminent attacks” on US embassies across the Middle East.

“I can reveal that I believe it probably would’ve been four embassies,” Trump said Friday.

On Sunday, Defense Secretary Mark Esper, however, said that he “had seen no intelligence forewarning of imminent attacks on embassies.”

The classified briefing was supposed to be given by senior State Department officials, including Brian Hook, the State Department's special representative for Iran, and David Schenker, the assistant secretary of State for the Middle East.

Citing a House aide, the news website Politico reported congressional staff are “furious.”

“This briefing is required by law every month, and today's was the most important we've had scheduled in a long time. The State Department has given us no explanation whatsoever,” the aide said.

A Senate aide also said the administration “will vaguely claim it was a logistical issue, even though this briefing had been already locked into the schedule for days.”

House Democrats have already criticized Secretary of State Mike Pompeo who refused to appear for a public hearing earlier this week.

On January 3, a US drone strike at Baghdad’s international airport assassinated Lieutenant General Qassem Soleimani, the commander of the Quds Force of the Islamic Revolution Guards Corps (IRGC), and Abu Mahdi al-Muhandis, the second-in-command of Iraq’s Popular Mobilization Units (PMU), as well as eight other people.

Both commanders were admired by Muslim nations for their role in eliminating the Takfiri terrorist group of Daesh in the region, particularly in Iraq and Syria.