(CNN) President Donald Trump positioned himself squarely against the leadership of the FBI and Department of Justice on Friday ahead of the possible release of a highly controversial Republican memo alleging the FBI abused its surveillance tools, claiming the government agencies "politicized the sacred investigative process in favor of Democrats and against Republicans."

Trump, by accusing the leadership of having a bias against Republicans, is once again maligning people he appointed to their roles, including FBI Director Christopher Wray, a man Trump nominated after he fired former FBI Director James Comey in May.

The tweet also puts Trump squarely on the side of Republican lawmakers who view the memo, which was penned by House Intelligence Chairman Devin Nunes and approved for release by the House committee earlier this week, as a document that shows evidence of nefarious motives atop the FBI.

"The top Leadership and Investigators of the FBI and the Justice Department have politicized the sacred investigative process in favor of Democrats and against Republicans - something which would have been unthinkable just a short time ago," Trump wrote. "Rank & File are great people!"

The tweet is especially notable since Trump once argued the FBI's mistreatment of a Democrat, Hillary Clinton, in its handling of the investigation into her email server led him to fire Comey. The President, however, would later say that he considered "this Russia thing" before dismissing the FBI director.

Read More