The White House is actively discussing possible replacements for Defense Secretary James Mattis, according to a report published in The Washington Post on Wednesday.
The newspaper reported that discussions about who would succeed the top Trump administration official predated reports this week that Mattis had insulted the president's intelligence. One senior administration official told the paper, however, that "speculation about who replaces Mattis is now more real than ever."
On Tuesday, The Washington Post published excerpts from "Fear," a forthcoming book written by Bob Woodward. Mattis told associates that the president had the understanding of "a fifth- or sixth-grader," Woodward wrote.
Wednesday's report was written by Josh Rogin, a national security columnist for the newspaper. The Department of Defense did not immediately respond to a request for comment from CNBC. Mattis has called the claims in Woodward's book "fiction."
The president, who has vigorously attacked Woodward's book, stood by Mattis on Wednesday, telling reporters that the former United States Marine Corps general is staying on board.
At the top of the list to succeed Mattis is retired four-star Army Gen. Jack Keane, according to the report. Keane, a frequent guest on Fox News, was tapped for the top job before Mattis, Keane has said. Keane declined due to family issues, and recommended Mattis for the role.
Keane did not immediately respond to a request for comment from CNBC.
Other possible contenders are Sen. Tom Cotton, R-Ark., Sen. Lindsey Graham, R-S.C., businessman and former Treasury Department official David McCormick and former Missouri Sen. Jim Talent.
Kevin Bishop, a spokesperson for Graham, said the White House had not reached out about the post.
"He's never expressed any interest whatsoever in a Cabinet position," Bishop said.
Cotton, McCormick and Talent did not immediately respond to requests for comment from CNBC left with their representatives.
— CNBC's Brian Schwartz contributed to this report.
Correction: Sen. Tom Cotton is a Republican from Arkansas. An earlier version misidentified his state.