(Image source from: Washington Post)

The White House is actively discussing possible replacements for James Mattis, Defense Secretary, 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."

The Washington Post on Tuesday 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 claims in Woodward's book was called the "fiction" by Mattis.

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 General Jack Keane, according to the report. Keane, a prevailing invitee on Fox News, was tapped for the top job before Mattis, Keane has said. Keane declined due to household issues and recommended Mattis for the office.

Other possible contenders are Sen. Tom Cotton, R-Ark., Senator 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.

By Sowmya Sangam