US President Donald Trump said his former security advisor John Bolton turned out to be 'grossly incompetent, and a liar'.

"I gave John Bolton, who was incapable of being Senate confirmed because he was considered a wacko, and was not liked, a chance. I always like hearing differing points of view. He turned out to be grossly incompetent, and a liar. See judge’s opinion. CLASSIFIED INFORMATION!!!" Trump tweeted.

John Bolton's book 'The Room Where It Happened' is set to be released on June 23.

According to the Justice Department, there were classified items that remained in the book, including some as "exceptionally restricted." Trump had earlier said that every conversation with him is "highly classified."

Federal prosecutors are weighing whether to criminally charge John Bolton with disclosing classified information or not.