WASHINGTON — President Trump threatened legal fire and fury on Thursday in an effort to block a new book portraying him as a volatile and ill-equipped chief executive, but the publisher defied his demand to halt its release and instead moved up its publication to Friday because of soaring interest.

Angry at the publisher’s refusal to back down, Mr. Trump took aim late Thursday night at the book’s author, Michael Wolff, and one of his primary sources, Stephen K. Bannon, the former White House chief strategist, whose derisive comments about the president and his family stirred deep resentment in the Oval Office.

“I authorized Zero access to White House (actually turned him down many times) for author of phony book!” Mr. Trump wrote on Twitter shortly before 11 p.m. “I never spoke to him for book. Full of lies, misrepresentations and sources that don’t exist. Look at this guy’s past and watch what happens to him and Sloppy Steve!”

The president’s blast at Mr. Wolff came at the end of a day in which Mr. Trump’s effort to stop publication failed. In an 11-page letter sent in the morning, a lawyer for the president said the book, “Fire and Fury: Inside the Trump White House,” as excerpted in a magazine article, includes false statements about Mr. Trump that “give rise to claims for libel” that could result in “substantial monetary damages and punitive damages.”

“Mr. Trump hereby demands that you immediately cease and desist from any further publication, release or dissemination of the book, the article, or any excerpts or summaries of either of them, to any person or entity, and that you issue a full and complete retraction and apology to my client as to all statements made about him in the book and article that lack competent evidentiary support,” the letter said.

Undeterred, Henry Holt and Co., the publisher, announced that instead it would make the book available for sale starting at 9 a.m. Friday rather than wait for its original release date on Tuesday. “We see ‘Fire and Fury’ as an extraordinary contribution to our national discourse, and are proceeding with the publication of the book,” the company said in a statement.

The book infuriated Mr. Trump in part by quoting Mr. Bannon making derogatory comments about the president’s children. Mr. Bannon was quoted as saying that Donald Trump Jr. had been “treasonous” and “unpatriotic” for meeting with Russians during the 2016 campaign and that Ivanka Trump was “dumb as a brick.” Mr. Trump fired back on Wednesday, saying that Mr. Bannon had “lost his mind” and had “nothing to do with me or my presidency.”

Mr. Bannon, who had stayed in touch with Mr. Trump sporadically after being pushed out of the White House last summer, sought to smooth over the rift during his Breitbart News radio show on Wednesday night.

When a caller said that Mr. Trump had “made a huge mistake, Steve, bashing you like he did,” Mr. Bannon brushed it aside. “The president of the United States is a great man,” Mr. Bannon said. “You know I support him day in and day out, whether going through the country giving the ‘Trump Miracle’ speech or on the show or on the website.”

The president cited those comments on Thursday morning when asked by reporters if Mr. Bannon had betrayed him. “I don’t know,” Mr. Trump said. “He called me a great man last night so, you know, he obviously changed his tune pretty quick.”

Although he responded to Mr. Bannon’s flattery, that did not mean Mr. Trump was ready to forgive, as his late-night tweet made clear. About a half-hour later, Donald Trump Jr. seized on his father’s new nickname for the famously rumpled and often unshaven Mr. Bannon in his own tweet. “I have a feeling #SloppySteve is going to go big,” Donald Jr. wrote. “Branding gold.”

Mr. Trump’s spokeswoman earlier in the day made clear that the president wanted Mr. Bannon punished for his disloyalty. Asked at her daily briefing whether Breitbart News should fire Mr. Bannon, Sarah Huckabee Sanders, the White House press secretary said, “I certainly think that it’s something they should look at and consider.”

Through a long career in real estate and entertainment, Mr. Trump has repeatedly threatened lawsuits against authors, journalists and others who angered him, but often has not followed through, including after such a threat against The New York Times during the 2016 presidential campaign, and it was unclear whether he would in this case, either.

Mr. Wolff did not reply to a request for comment, but after his publisher moved up the release, he jabbed at Mr. Trump on Twitter. “Here we go,” he wrote. “You can buy it (and read it) tomorrow. Thank you, Mr. President.”

Most presidents have avoided legal confrontations over unflattering publications out of fear of giving them more publicity and promoting sales, but it is not unprecedented. Former President Jimmy Carter, shortly after leaving the White House, threatened to sue The Washington Post over a gossip column item asserting that his administration had bugged Blair House, the government guest quarters, while Nancy and Ronald Reagan stayed there before the 1981 inauguration. The Post retracted the item and Mr. Carter dropped the matter.

Mr. Trump’s threat generated a debate among advocates and legal scholars. “The president’s attempt to halt publication of a book because of its content is flagrantly unconstitutional,” said Suzanne Nossel, the executive director of PEN America, a group that defends free expression around the world.

The bar for any legal action by a president, the most public of public figures, is particularly high. “At the center of any libel case has got to be an actual statement of fact that’s alleged to be inaccurate and damaging,” said Bruce W. Sanford, a veteran media law specialist at BakerHostetler. “You can’t just say we don’t like this book and all the things in it and sue for libel. That’s not what libel cases are about.”

The book, which quickly shot up to No. 1 on Amazon’s best-seller list after articles about it on Wednesday, presents Mr. Trump as an unengaged candidate and president who grew bored when an aide tried to explain the Constitution to him and refuses to read even one-page briefing papers.

Advisers are reported to have called the president an “idiot,” a “dope” or “dumb” as dirt, and Melania Trump is described as being so unhappy about the prospect of life in the White House that she was in tears on election night. Mrs. Trump has disputed the characterization, and spokesmen for Treasury Secretary Steven Mnuchin; Gary D. Cohn, the national economics adviser; and Lt. Gen. H. R. McMaster, the national security adviser, all denied the disparaging quotes attributed to them.

Charles J. Harder, the president’s lawyer, has represented Mrs. Trump and other high-profile figures in cases against the news media. Based in Beverly Hills, Calif., he won Hulk Hogan’s landmark invasion-of-privacy case against Gawker Media and until recently represented Harvey Weinstein, the Hollywood mogul. Mr. Harder threatened to sue The New York Times over an article documenting sexual harassment by Mr. Weinstein. But Mr. Harder no longer represents Mr. Weinstein, and no lawsuit has been filed.

In his letter to Mr. Wolff and his publisher, Mr. Harder said the book itself admits “that it contains untrue statements.” In an author’s note, Mr. Wolff writes that many of the accounts that he collected “are in conflict with one another; many, in Trumpian fashion, are baldly untrue.” He said he sometimes “let the players offer their versions, in turn allowing the reader to judge them,” and in other instances “settled on a version of events I believe to be true.”

Mr. Harder argued that that proves actual malice and reckless disregard for the truth, standards that courts use to judge whether a public person has been libeled. Mr. Harder cited no specific statements that he judged untrue.

But some people cited in the book have disputed episodes describing them. Former Prime Minister Tony Blair of Britain denied suggesting to Jared Kushner, the president’s son-in-law and senior adviser, that British intelligence might have spied on Mr. Trump’s campaign. “This story, as we have pointed out, is a complete fabrication,” he told BBC Radio 4. “I mean literally, from beginning to end. I’ve never had such conversations, in the White House, outside the White House, with Jared Kushner, with anybody else.”

Asked on Thursday for examples of potentially libelous inaccuracies in the book, Ms. Sanders cited only an anecdote in which Mr. Trump seemed not to recognize the name of former Speaker John A. Boehner, even though he had previously posted on Twitter about the lawmaker.

“There are numerous mistakes,” she said, “but I’m not going to waste my time or the country’s time going page by page, talking about a book that’s complete fantasy and just full of tabloid gossip.”