WASHINGTON — The top U.S. military officer told Congress on Tuesday that he knew former President Trump wasn’t planning to attack China and that it was his job to reassure the Chinese of that fact in the phone calls that have triggered outrage from some lawmakers.

Army Gen. Mark Milley, chairman of the Joint Chiefs of Staff, delivered a vehement defense of two calls he made to his Chinese counterpart, saying he was responding to “concerning intelligence” that China was worried about a U.S. attack.

“I know, I am certain, that President Trump did not intend to attack the Chinese. … And it was my directed responsibility by the secretary to convey that intent to the Chinese,” Milley told the Senate Armed Services Committee. “My task at that time was to de-escalate. My message again was consistent: Stay calm, steady, and de-escalate. We are not going to attack you.”

Milley has been at the center of controversy after reports that he made two calls to Gen. Li Zuocheng of the People’s Liberation Army to assure him that the United States was not suddenly going to go to war with or attack China. Details of the calls were first aired in excerpts from the recently released book “Peril” by Washington Post journalists Bob Woodward and Robert Costa.

Some U.S. lawmakers have said Milley overstepped his authority, and they have called for President Biden to fire him. Trump blasted Milley as treasonous, called him “a complete nutjob” and said Milley “never told me about calls being made to China.”

In his most extensive comments to date on the matter, Milley said the calls on Oct. 30 and Jan. 8 were fully coordinated with the defense secretaries at the time as well as other U.S. national security agencies. And he said that such military-to-military communications are critical to prevent war between great powers that possess nuclear weapons.

The calls came during Trump’s turbulent last months in office as he challenged the results of the 2020 election. The second call came two days after Jan. 6, when a violent mob attacked the U.S. Capitol in an effort to prevent Congress from certifying Biden’s White House victory.

Milley said the October call was made at the direction of then-Defense Secretary Mark Esper and the second was done at the request of the Chinese and coordinated with then-acting Defense Secretary Chris Miller’s office.

Milley also addressed a call he received from House Speaker Nancy Pelosi. He said Pelosi “called me to inquire about the president’s ability to launch nuclear weapons. I sought to assure her that nuclear launch is governed by a very specific and deliberate process.”

He said he assured her that while the president is the sole nuclear launch authority, “he doesn’t launch them alone.” He said that as chairman he is part of the launch decision process.

“There are processes, protocols and procedures in place, and I repeatedly assured her there is no chance of an illegal, unauthorized or accidental launch,” Milley said.

The book asserts that during the call, Milley agreed with Pelosi’s statement that Trump was suffering a mental decline after the election. During Tuesday’s hearing, Milley appeared to discount that, saying “I am not qualified to determine the mental health of the president of the United States.”

He said that after the call was over, he had a short meeting with staff to go over the process. He also said he informed Miller of the call at the time.

“At no time was I attempting to change or influence the process, usurp authority or insert myself in the chain of command, but I am expected, I am required, to give my advice and ensure that the president is fully informed,” Milley said.

The issue of his calls did not come up in the Senate hearing until nearly three hours into the session. Milley was asked if he spoke with the book’s authors and he said he did talk with Woodward. Asked if he was “accurately represented” in the book, Milley said he hasn’t read it, but has seen press reporting on it. Sen. Marsha Blackburn, R-Tenn., said she would get back to him once he has read the book.