Updated

The CIA's top officer on the ground in Libya at the time of the Benghazi terror attack will appear before a House panel for the first time Tuesday afternoon -- to deliver what could be critical closed-door testimony, ahead of ex-CIA Director Michael Morell's scheduled appearance on Wednesday.

Two congressional sources confirmed to Fox News that the CIA chief of station will appear before a House intelligence subcommittee. His perspective was long-sought by lawmakers, and the timing is critical -- coming before Morell's first-ever public testimony Wednesday about his role, and that of the administration, in the flawed "talking points" which blamed a protest.

Lawmakers want to hear from the chief of station because, according to a Senate Intelligence Committee report, he wrote to Morell and other CIA leadership on Sept. 15, 2012, emphasizing in an email that the attacks were "not/not an escalation of protests." A day later, then-U.N. Ambassador Susan Rice went on national television and said the opposite.

As first reported by Fox News, Morell is facing accusations he downplayed, or even dismissed, the reporting of U.S. personnel on the ground in Libya, including the chief of station.

According to a source with first-hand knowledge of events, during a secure video conference call two days after the Sept. 11, 2012 attack, Morell told the team in Libya that there was intelligence a demonstration preceded the assault. Fox News is told that based on communications with CIA headquarters, the chief of station understood as early as Sept. 13, 2012, that the burden was on him to prove that there was no protest.

Both the House Oversight and Investigations Subcommittee and the CIA public affairs office declined to comment.

Morell, meanwhile, is also appearing for public testimony after facing accusations by Republicans of misleading lawmakers over his role in the talking points. He initially claimed the talking points, before Rice's interview appearances, were provided to White House officials for awareness and not for their input. Emails later released show administration involvement began at the earliest stages, and Morell personally cut 50 percent of the text.

In an exchange on Feb. 27, a CIA spokesman provided the following statement to Fox News about Morell and the talking points, suggesting the issue was settled:

"As we have said multiple times, the talking points on Benghazi were written, upon a request from Congress, so that members of Congress could say something preliminary and in an unclassified forum about the attacks. As former CIA Deputy Director Michael Morell has stated publicly time and again, the talking points were never meant to be definitive and, in fact, the points themselves noted that the initial assessment may change. He has addressed his role in the talking points numerous times. We don't have anything further to add to the large body of detail on the talking points that is already in the public domain."

Separately, a State Department inspector general report released on Tuesday examined another controversy that has persisted in the wake of the 2012 attack -- the level of security at some of the State Department's riskiest posts.

Noting that embassies "have long been a target of attacks against the United States," the audit asked overseas security officials about the process for requesting security funding. While most said the system was clear, "a significant number of post security officials believed the processes were unclear and difficult and expressed dissatisfaction with the timeliness or sufficiency of the responses received to their formal requests for physical security funding."

Fox News' Catherine Herridge contributed to this report.