TEHRAN - Former Defense Secretary Mark T. Esper on Sunday sued the Pentagon, accusing officials of improperly blocking significant portions of an upcoming memoir about his tenure under President Donald J. Trump.

Esper, who served as defense secretary from July 2019 until being fired by Trump in November, filed a lawsuit against the Pentagon on Sunday, contending it is “improperly” withholding “significant text” from his memoir - A Sacred Oath- "under the guise of classification."

Esper said in a statement that his goal with the book, which is expected to be published in May, was to give the public “a full and unvarnished accounting of our nation’s history, especially the more difficult periods.”

 “I am more than disappointed the current administration is infringing on my First Amendment constitutional rights. And it is with regret that legal recourse is the only path now available for me to tell my full story to the American people.” He added.

“The withheld text is crucial to telling important stories discussed in the Manuscript,” the lawsuit reads.

The book, chronicles Esper’s experience in what he described as a “tumultuous second half of the Trump administration.”

Esper claimed in a statement that his goal is to give the public “a full and unvarnished accounting of our nation’s history, especially the more difficult periods.”

Defense officials redacted 60 pages of his memoir and told him not to quote Trump and others in meetings or mention their conversations. He wrote that his tenure was “an unprecedented time of civil unrest, public health crises, growing threats abroad, Pentagon transformation, and a White House seemingly bent on circumventing the Constitution.”

He said in the lawsuit that the Pentagon is unlawfully imposing restraint on his book by “delaying, obstructing and infringing on his constitutional right to publish” his book.

He noted defense officials redacted 60 pages of his memoir and told him not to quote Trump and others in meetings or mention their conversations. He added officials also asked him not to use certain nouns and verbs while writing about historical events in the book.

John F. Kirby, the Pentagon’s chief spokesman, said the agency was aware of Mr. Esper’s concerns. “As with all such reviews, the department takes seriously its obligation to balance national security with an author’s narrative desire,” Kirby said. “Given that this matter is now under litigation, we will refrain from commenting further.”

Esper and Trump clashed over using the military to corral demonstrators protesting the police murder of Black George Floyd last June. Trump accused him of not being sufficiently loyal while Esper claimed he was trying to keep his department politically neutral.

Esper is among the most senior former government officials, if not the most senior, to sue for prior restraint related to a book. The lawsuit came a year after a presidential campaign in which President Biden promised to restore the norms that had been tossed aside by his predecessor.

Executive branch employees — ranging from senior officials like the secretary of state and the national security adviser to low-level ones like federal prosecutors and agents — have to submit their manuscripts to the prepublication review process. That process is intended to prevent materials that may damage national security from becoming public while protecting the author’s First Amendment rights.

In cases where an agency or a department has an issue with information being revealed, that section of the book is supposed to be removed or edited to obscure the problematic content.