WATCH: Fox News' Shep Smith blasts Trump for failing British allies on Russian poisoning

Though disagreement about the Iran nuclear deal was the apparent cause for Secretary of State Rex Tillerson's firing, a disagreement about who caused a former Russian spy to fall ill from a poisoning also foreshadowed his abrupt ouster.

Responding to the ex-Russian spy poisoning scandal — which both Tillerson and the UK have blamed on Russia while President Donald Trump reserves judgement — Fox News host Shep Smith was incredulous.

"As soon as we get the facts straight, if we agree with them, we will condemn Russia or whoever it may be," Trump said during a press conference earlier in the day.

"Information like that, intelligence like that — it's all one thing," the Fox News host said. "That doesn't make sense."

The Associated Press' Josh Lederman, who was on the plane with Tillerson when he returned to D.C. from Africa a day early in the hours prior to being publicly fired, said Trump's message was very different from the secretary of state's.

Tillerson, the AP reporter continued, noted that the poison used on the former Kremlin spy "clearly came from Russia."

"Tillerson seemed eager to actually go after Russia and described this as part of a broader pattern of increasing Russian aggression," Lederman continued. "Yet at the White House we hear a lot more caution about drawing any conclusions about this incident."

Smith noted that the president and the White House have paid lip service to "standing by" British Prime Minister Theresa May, who strongly condemned Russian President Vladimir Putin for the poisoning, but have not acted accordingly.

"What you say is one thing," the host concluded, "but what they're doing is really not that."

Watch below, via Fox News: