President Biden on Wednesday threw his full support behind the Pentagon’s top uniformed officer, who has come under fire after a new book revealed he privately conferred with his Chinese counterpart to avert armed conflict late in the Trump administration.

“I have great confidence in General Milley,” Biden told reporters at the White House, following calls from former president Donald Trump and his Republican allies on Capitol Hill for the removal of Gen. Mark A. Milley as chairman of the Joint Chiefs of Staff.

Biden’s declaration, coinciding with efforts by the chief spokespersons for the White House and the Pentagon to stage a similar defense of the embattled general, effectively ends speculation that Milley’s assignment may be cut short. But the controversy surrounding his fitness for the job rages on — and thus far is falling mostly along party lines.

On Sept. 15, White House press secretary Jen Psaki said President Biden had “complete confidence” in Chairman of the Joint Chiefs of Staff, Gen. Mark A. Milley. (The Washington Post)

According to the book from Washington Post associate editor Bob Woodward and national political reporter Robert Costa, Milley spoke with Gen. Li Zuocheng of the People’s Liberation Army twice: once in late October and again in early January, after Trump’s supporters laid siege to the U.S. Capitol in an attempt to overturn his election defeat. The domestic upheaval had shaken the government in Beijing, where leaders, according to the book’s authors, worried that Trump appeared to be acting so erratically that he might order an attack on China, triggering a war.

In their calls, Milley sought to reassure Li that things in the United States were “100 percent steady,” according to the book, even if “democracy can be sloppy sometimes.” But he later instructed Pentagon officials that he had to be involved in any discussions about launching nuclear weapons, even though it is the president who would give such an order, the authors wrote.

The blowback was instantaneous, with critics of Milley complaining he undercut his commander in chief and violated the principle of civilian control over the military. Trump, in denying he had ever contemplated attacking China, called the general’s actions “treason.”

Long-running tension between the world powers, fueled by the United States’ objection to China’s expansionist posture in the South China Sea, worsened under Trump as a result of his often-belligerent rhetoric toward Beijing and threats to pull the countries into an economically ruinous trade war.

Col. Dave Butler, a spokesman for Milley, issued a statement Wednesday largely confirming what’s disclosed in the book, “Peril,” set for release next week, and saying that Milley had acted constitutionally and within his established responsibilities. The general, Butler said, “continues to act and advise within his authority in the lawful tradition of civilian control of the military and his oath to the Constitution.”

Milley’s apparent efforts to go outside the chain of command have angered not only the former president and his supporters but even some of his critics.

Sen. Marco Rubio (Fla.), the Senate Intelligence Committee’s top-ranking Republican, demanded in a letter to Biden that he fire Milley for having “worked to actively undermine the sitting Commander in Chief” and having “contemplated a treasonous leak of classified information” to the Chinese government, an apparent reference to reporting in the book that Milley promised Li he would alert him beforehand if U.S. forces were ordered to attack.

Alexander Vindman, a retired Army officer who was one of the key witnesses against Trump during his first impeachment, also called for Milley’s removal because he “usurped civilian authority, broke Chain of Command, and violated the sacrosanct principle of civilian control over the military.”

“It’s an extremely dangerous precedent. You can’t simply walk away from that,” Vindman said on Twitter.

Chris Miller, Trump’s acting defense secretary at the end of his administration, told Fox News on Wednesday that he “did not and would not ever authorize” Milley to have “secret” calls with his Chinese counterpart. Miller, too, called on the general to resign.

But the Pentagon — while refusing to comment on the veracity of the book’s claims — defended Milley’s actions Wednesday as “not uncommon at all.”

“I see nothing in what I’ve read that would cause any concern,” Pentagon spokesman John Kirby told reporters, adding that “it is not only common, it’s expected” that Milley or any chairman of the Joint Chiefs would have conversations with his counterparts in adversary nations “to reduce the risk of miscalculation and conflict.”

John Bolton, who served as national security adviser under Trump, also came to Milley’s defense.

“His patriotism is unquestioned,” Bolton said in a statement, noting that Milley would have been under enormous pressure after November’s election as Trump refused to accept his loss. He said he would be “very surprised” if others in national security roles “were not fully aware of General Milley’s actions” and “fully concurred in them.”

Among the revelations in the book is a Jan. 8 conversation between Milley and House Speaker Nancy Pelosi (D-Calif.), in which she opined that Trump was “crazy” and ought to be arrested for his role in inspiring the Capitol riot on Jan. 6. Milley responded: “I agree with you on everything,” the authors wrote.

The controversy has amplified the scrutiny facing Biden, Milley and other senior military leaders over the U.S. military’s withdrawal from Afghanistan, which Republicans and some Democrats have criticized as chaotic and disappointing. Milley is due to testify about the deadly evacuation effort at a hearing of the Senate Armed Services Committee later this month, where he is also certain to face questions about his conversations with the Chinese general.

Though Republicans have echoed Rubio’s sentiments that Milley’s actions constitute a fireable offense, leading Democrats have called them defensible and necessary.

“It is breathtaking to think of the lengths that Milley and others went to avert the disasters Trump was creating at the end of his presidency,” Sen. Richard J. Durbin (D-Ill.) told reporters, adding that he was “not at all” concerned if Milley had overstepped his authority.

“It is a shame we reached that point in America’s history that’s necessary, and I think he did the responsible thing to keep America out of war,” Durbin said.

Isaac Stanley-Becker contributed to this report.

Correction

A previous version of this article mistakenly referred to China’s Gen. Li Zuocheng of the People’s Liberation Army as Zuocheng on second reference. He should have been referred to as Li. This version has been corrected.