The top Democrat on the House Oversight Committee is pushing the Republican chairman to request documents related to a report suggesting President Trump may have fired FBI Director James Comey to relieve mounting "pressure" from an FBI investigation into Russia's meddling in the 2016 campaign.

The report, from the New York Times, cited a document summarizing the meeting in which Trump told Russian officials visiting the White House last week that he no longer felt "great pressure" after firing Comey, who he reportedly called a "nut job." He also asserted that he is not under investigation.

Cummings said the report is "astonishing — and extremely troubling."

The Maryland Democrat said if there is such a White House document, which the White House has yet to deny, that the oversight panel needs to obtain copies immediately.

"Chairman [Jason] Chaffetz should request these White House documents today and have his subpoena pen ready — just as he did earlier this week with the memos written by Director Comey."

The reference to a "subpoena pen" is a nod to a comment made by Chaffetz, R-Utah, earlier in the week, who threatened to use his subpoena power to obtain a memo from Comey, revealed in a separate report, that said Trump pressured him to drop a probe into ousted national security adviser Mike Flynn.