WASHINGTON — The chairman of the Joint Chiefs of Staff, Gen. Charles Q. Brown Jr., said Monday that U.S. “credibility is at stake” with each of its alliances, including NATO, which former President Donald Trump disparaged in recent remarks.

In an interview with NBC “Nightly News” anchor Lester Holt at the Pentagon, Brown was asked what he thinks about Trump‘s suggesting that he would allow Russia to have its way with NATO members if they don’t contribute enough to the alliance.

“This year is the 75th anniversary of NATO,” Brown said in the interview airing Monday night. “And I think we have a responsibility to uphold those alliances. U.S. credibility is at stake with each of our alliances, and U.S. leadership is still needed, wanted and watched.”

He said that’s the message he communicates to NATO countries, “realizing that each one of us has political leadership that we have to work with, and that they set the agenda.”

In a Truth Social post Monday afternoon, Trump appeared to double down on his earlier comments indicating he would let Russia do “whatever the hell they want” to NATO countries that don’t pay a specific amount of their gross domestic product toward defense spending.

He said in all caps that NATO “has to equalize,” adding, “They will do that if properly asked. If not, America first!”

Asked whether Trump’s comments alarmed him, Brown said: “What I do is I focus on continuing to build and strengthen our relationship with NATO. And I realize there’ll be various dialogue in discussions at the political level. My job is to make sure that we are doing everything we can with our NATO allies on the military aspect, and I’ll continue to do that throughout.”

At a rally in South Carolina on Saturday, Trump said he would urge Russia “to do whatever the hell they want” if it attacked a NATO country that didn’t pay enough toward the alliance.

“Let’s say that happened. No, I would not protect you. In fact, I would encourage them to do whatever the hell they want,” he said. “You got to pay your bills.”

A spokesman for President Joe Biden’s re-election campaign criticized Trump’s remarks in a statement Monday.

“Donald Trump encouraged Russia’s ruthless dictator to attack our allies and fellow Western democracies,” spokesman TJ Ducklo said, “rightly sparking outrage across Europe and among those fighting for democracy around the world.”

As president, Trump railed against NATO and countries that don’t pay the agreed-upon 2% of their gross domestic product toward defense spending for the alliance. He also questioned Article 5 of NATO’s charter, which is an agreement that an attack on one is an attack on all and would be met with a collective response.

Separately, Brown defended Biden’s mental acuity after the special counsel overseeing Biden’s mishandling of classified documents suggested he had a “poor memory” at times.

“He’s pretty sharp,” Brown said. “You know, he’s got a very good grasp of the issues. … I even got mentored as I came in and sat down with different folks that have worked very closely with the president ’cause I want to make sure I get it right. And I’ve seen him in the Oval [Office] call folks out if he’s not getting the information he needs. … He’s sharp.”